Grain boundary engineering

ABSTRACT

This disclosure is directed to sintered bodies comprising grains and a grain boundary composition, wherein: (a) the grains comprise a composition substantially represented by a formula G 2 M 14 B, where G is Nd, Dy, Pr, Tb, or a combination thereof, and M is Co, Fe, Ni, or a combination thereof, wherein the grains are optionally doped with one or more rare earth elements; and (b) the grain boundary composition is an alloy composition substantially represented by the formula: Nd 8.5-12.5 Dy 35-45 Co 32-41 Cu 3-6.5 Fe 1.5-5 , wherein the subscript values are atom percent relative to the total composition of the alloy composition. Corresponding populations of particles are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/093,971, filed Apr. 8, 2016, which claims priority to U.S. patentapplication Ser. No. 14/742,080, filed Jun. 17, 2015, now U.S. Pat. No.9,336,932 that issued May 10, 2016, which claims priority to U.S.Provisional Application No. 62/037,754, filed Aug. 15, 2014, thecontents of which are incorporated herein by reference in theirentireties for all purposes.

BACKGROUND

The present disclosure relates to the manufacture of aNeodymium-Iron-Boron (Nd—Fe—B) sintered magnet using Grain BoundaryEngineering (GBE).

The global market for Rare Earth Permanent Magnets (REPM) is growingtogether with the range of REPM applications. REPM's exhibit highmagnetic performance characteristics, and are used in the development ofhigh-tech, high-efficiency applications in many industries includingelectronics, energy, transportation, aerospace, defense, medicaldevices, and information and communication technology.

For example, applications using the Nd—Fe—B permanent magnets include:starter motors, anti-lock braking systems (ABS), fuel-pumps, fans,loudspeakers, microphones, telephone ringers, switches, relays,hard-disk drives (HDD), stepper motors, servo-motors, magnetic resonanceimaging (MRI), windmill generators, robotics, sensors, magneticseparators, guidance systems, satellites, cruise missiles, and so on.

The Nd—Fe—B type sintered magnet has a very fine tuned elementalcomposition, which includes, besides Nd, elements like Dy, Tb, Ga, Co,Cu, Al and other minor transitional metal elemental additions.

The use of heavy rare earth Dysprosium (Dy) may help to improve thetemperature resistance of Nd—Fe—B magnets. Despite itsperformance-boosting characteristics, Dy resources are limited. Dysupply risk and scarcity cause a shortage of high temperatureperformance Nd—Fe—B magnets which can be used in energy-saving motorapplications.

The present disclosure for Grain Boundary Engineering reduces the Dycontent in the Nd—Fe—B product while maintaining high performance,increasing temperature resistance, and lowering production cost.

SUMMARY

A process may include creation of an Nd2Fe14B permanent magnet withspecific performance characteristics, such as desired combinations ofparticle size, alignment, density, energy product (BHmax), remanence(Br), and coercivity (iHc). For instance, a Grain Boundary Engineering(GBE) process may include the production of Nd—Fe—B permanent magnetswith a grain boundary modified rich phase. A GBE process may create newmagnets from new magnetic material, e.g., that has not previously beenused in a consumer product, from recycled magnetic material, e.g., thatwas previously used in a consumer product, or both.

The GBE process maintains an original grain phase of starting magneticmaterial, while modifying a grain boundary phase of the startingmagnetic material. For instance, when creating a new Nd2Fe14B magnet, aGBE system keeps, from the starting material, at least 90 vol. % of theNd—Fe—B 2:14:1 phase grains in a final magnetic product. A GBE systemmay replace all or substantially all of an Nd-rich grain boundary phasewith a new grain boundary phase made from additive material. In someexamples, a GBE system maintains between about 90 to about 97 vol. % ofthe starting grains in a final magnetic product. In some examples, a GBEsystem replaces between about 3 to about 12 vol. % of the Nd-rich grainboundary phase with the new grain boundary phase.

In general, one innovative aspect of the subject matter described inthis specification can be embodied in methods that include the actionsof melting magnetic elements to create a molten alloy, forming, from themolten alloy, cast alloy flakes that include a plurality of 2:14:1 phasegrains, pulverizing the cast alloy flakes to create a first powder whilemaintaining at least some of the 2:14:1 phase grains from the cast alloyflakes, pressing and aligning particles in the first powder to create afirst compact, sintering the first compact to create a sintered compact,fragmenting the sintered compact to form a second powder whilemaintaining at least some of the 2:14:1 phase grains from the sinteredcompact, mixing the second powder with a) a rare earth material R and b)an elemental additive A to produce a homogeneous powder whilemaintaining at least some of the 2:14:1 phase grains from the secondpowder, wherein the rare earth material R includes at least one, atleast two, or all three of: i) Nd, ii) Pr, or iii) Dy, and the elementaladditive A includes at least one, at least two, or all three of: i) Co,ii) Cu, or iii) Fe, and sintering and magnetizing the homogeneous powderto form an Nd—Fe—B magnetic product. Other embodiments of this aspectinclude corresponding computer systems, apparatus, and computer programsrecorded on one or more computer storage devices, each configured toperform the actions of the methods. A system of one or more computerscan be configured to perform particular operations or actions by virtueof having software, firmware, hardware, or a combination of theminstalled on the system that in operation causes or cause the system toperform the actions. One or more computer programs can be configured toperform particular operations or actions by virtue of includinginstructions that, when executed by data processing apparatus, cause theapparatus to perform the actions.

The foregoing and other embodiments can each optionally include one ormore of the following features, alone or in combination. Forming, fromthe molten alloy, the cast alloy flakes that include the plurality of2:14:1 phase grains may include forming, from the molten alloy, castalloy flakes that each include a plurality of 2:14:1 phase grains. Therare earth Material R and the elemental additive A, together, may beNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. %.

In some implementations, fragmenting the sintered compact includesfragmenting the sintered compact to an average particle size between 1to 4 microns. Fragmenting the sintered compact to form the second powdermay include removing, from the second powder, particles with a particlefraction size bigger than an average size of particles in the secondpowder to obtain an oxygen concentration of less than 1.98 at. % in theNd—Fe—B magnetic product. Fragmenting the sintered compact to form thesecond powder may include fragmenting the sintered compact to form thesecond powder with an average particle size between about 1 micron toabout 2 millimeters, the method including further fragmenting the secondpowder to an average particle size between about 1 to about 4 microns,and homogenizing the second powder. Homogenizing the second powder mayinclude homogenizing the second powder that includes an average particlesize between about 1 micron to about 2 millimeters, and mixing thesecond powder with a) the rare earth material R and b) the elementaladditive A to produce the homogeneous powder may include mixing thesecond powder with an average particle size between about 1 to about 4microns with a) the rare earth material R and b) the elemental additiveA to produce the homogeneous powder. Mixing the second powder with a)the rare earth material R and b) the elemental additive A to produce thehomogeneous powder may include mixing the second powder with an averageparticle size between about 1 micron to about 2 millimeters with a) therare earth material R and b) the elemental additive A to produce thehomogeneous powder, and homogenizing the second powder may includehomogenizing the second powder that includes an average particle sizebetween about 1 to about 4 microns.

In some implementations, fragmenting the rare earth material R and theelemental additive A separately from fragmenting the sintered compact toform the second powder, wherein mixing the second powder with a) therare earth material R and b) the elemental additive A to produce thehomogeneous powder includes mixing the second powder with a) thefragmented rare earth material R and b) the fragmented elementaladditive A to produce the homogeneous powder. An atomic percentage of Coin the Nd—Fe—B magnetic product may be less than or equal to 3.098 at.%. An atomic percentage of Cu in the Nd—Fe—B magnetic product may beless than or equal to 0.1849 at. %. A combined atomic percentage of Feand Co in the Nd—Fe—B magnetic product may be between about 76.3928 andabout 83.1267 at. %. A combined atomic percentage of Fe and Co in theNd—Fe—B magnetic product may be less than or equal to 77 at. %. Acombined atomic percentage of Nd, Pr, and Dy in the Nd—Fe—B magneticproduct may be greater than or equal to a combined atomic percentage ofNd, Pr, and Dy in the sintered compact. A combined atomic percentage ofNd, Dy, and Pr in the Nd—Fe—B magnetic product may be less than or equalto 18 at. %.

In some implementations, mixing the second powder with a) the rare earthmaterial R and b) the elemental additive A to produce the homogeneouspowder includes homogeneously distributing the rare earth material R andthe elemental additive A within the second powder, and sintering andmagnetizing the homogeneous powder to form the Nd—Fe—B magnetic productincludes forming the Nd—Fe—B magnetic product with a concentration ofthe rare earth material R and a concentration of the elemental additiveA that increases, on average, surrounding the 2:14:1 phase grains withinthe Nd—Fe—B magnetic product. The method may include replacing an oldNd-rich grain boundary phase from the sintered compact and included inthe second powder with a new grain boundary phase that includes the rareearth material R and the elemental additive A.

In some implementations, the Nd—Fe—B magnetic product includes an amountof Nd in a range of [7.3635, 11.1038] (at. %), inclusive, an amount ofFe in a range of [76.3928, 80.0287] (at. %), inclusive, and an amount ofB in a range of [5.7493, 6.4244] (at. %), inclusive. The Nd—Fe—Bmagnetic product may include an amount of 0 in a range of [0.09, 4.0](at. %), inclusive, and an amount of C in a range of [0.01, 1.0] (at.%), inclusive. The Nd—Fe—B magnetic product may include an amount of Dyin a range of [0.199, 4.0535] (at. %), inclusive. The Nd—Fe—B magneticproduct may include an amount of Pr in a range of [1.445, 3.6323] (at.%), inclusive. The Nd—Fe—B magnetic product may include an amount of Coin a range of [0, 3.098] (at. %), inclusive. The Nd—Fe—B magneticproduct may include an amount of Cu in a range of [0.0508, 0.1849] (at.%), inclusive. A total amount of the rare earth material R in theNd—Fe—B magnetic product may be in a range of [12.66, 15.03] (at. %),inclusive.

In some implementations, the rare earth material R includes at least oneof i) an amount of Nd in a range of [6.1717, 11.8917] (at. %),inclusive, ii) an amount of Pr in a range of [1.5495, 4.821] (at. %),inclusive, or iii) an amount of Dy in a range of [0.2132, 5.3753] (at.%), inclusive, and the elemental additive A includes at least one of i)an amount of Co in a range of [0, 4.0948] (at. %), inclusive, ii) anamount of Cu in a range of [0.0545, 0.2445] (at. %), inclusive, or iii)an amount of Fe in a range of [81.1749, 85.867] (at. %), inclusive.These ranges are with respect to only the rare earth material R and theelemental additive A, and not the starting magnetic material, whetherunused or waste magnet material.

In some implementations, sintering and magnetizing the homogeneouspowder to form an Nd—Fe—B magnetic product includes sintering andmagnetizing the homogeneous powder to form the Nd—Fe—B magnetic productwith a remanence and a coercivity at least the same as the sinteredcompact. The coercivity of the Nd—Fe—B magnetic product may be betweenabout 0 to about 20% greater than the coercivity of the sinteredcompact. Sintering and magnetizing the homogeneous powder to form anNd—Fe—B magnetic product may include sintering and magnetizing thehomogeneous powder to form the Nd—Fe—B magnetic product with a finalremanence and a final coercivity, wherein the final remanence is about97% of another remanence of the sintered compact and the finalcoercivity is at least 30% greater than another coercivity of thesintered compact. Sintering and magnetizing the homogeneous powder toform an Nd—Fe—B magnetic product may include sintering and magnetizingthe homogeneous powder to form the Nd—Fe—B magnetic product with a finalremanence and a final coercivity, wherein the final remanence is about95% of another remanence of the sintered compact and the finalcoercivity is at least 80% greater than another coercivity of thesintered compact. Sintering and magnetizing the homogeneous powder toform an Nd—Fe—B magnetic product may include sintering and magnetizingthe homogeneous powder to form the Nd—Fe—B magnetic product with a finalremanence and a final coercivity, wherein the final remanence is about5% greater than another remanence of the sintered compact and the finalcoercivity is at least the same as another coercivity of the sinteredcompact.

In general, one innovative aspect of the subject matter described inthis specification can be embodied in a compound includingNd₁₋₂₀Dy₁₋₆₀Co₁₋₆₀Cu_(0.1-20)Fe_(0.5-90) at. %. The compound may beNd₇₋₁₄Dy₃₀₋₅₀Co₂₈₋₄₅Cu₁₋₁₀Fe₁₋₁₀ at. %. The compound may beNd_(8.5-12.5)Dy₃₅₋₄₅Co₃₂₋₄₁Cu_(3-6.5)Fe_(1.5-5) at. %. The compound maybe Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % at. %. Thecompound may include less than 0.12 at. % oxygen, less than 0.0058 at. %carbon, or both. In some examples, the compound may include between0.00009 to 0.18 at. % oxygen, or between 0.028 to 0.1 at. % oxygen. Insome examples, the compound may include between 0.0001 to 0.09 at. %carbon, or between 0.0058 to 0.009 at. % carbon.

In some implementations, the compound may consist essentially of therecited formula. For example, the compound may consist essentially ofNd₁₋₂₀Dy₁₋₆₀Co₁₋₆₀Cu_(0.1-20)Fe_(0.5-90) at. %,Nd₇₋₁₄Dy₃₀₋₅₀Co₂₈₋₄₅Cu₁₋₁₀Fe₁₋₁₀ at. %,Nd_(8.5-12.5)Dy₃₅₋₄₅Co₃₂₋₄₁Cu_(3-6.5)Fe_(1.5-5) at. %, orNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % at. %. Thecompound may include less than 0.12 at. % oxygen, less than 0.0058 at. %carbon, or both. In some examples, the compound may include between0.00009 to 0.18 at. % oxygen, or between 0.028 to 0.1 at. % oxygen. Insome examples, the compound may include between 0.0001 to 0.09 at. %carbon, or between 0.0058 to 0.009 at. % carbon.

In general, one innovative aspect of the subject matter described inthis specification can be embodied in a compound including at least oneof: i) an amount of Nd in a range of [6.1717, 11.8917] (at. %),inclusive, ii) an amount of Pr in a range of [1.5495, 4.821] (at. %),inclusive, or iii) an amount of Dy in a range of [0.2132, 5.3753] (at.%), inclusive, and an amount of Co in a range of [0, 4.0948] (at. %),inclusive, an amount of Cu in a range of [0.0545, 0.2445] (at. %),inclusive, and an amount of Fe in a range of [81.1749, 85.867] (at. %),inclusive. The compound may include a combination of Nd, Pr, and Dy in arange of [13.236, 16.407] at. %, inclusive. The compound may include atleast both Nd and Dy. The compound may include at least both Nd and Pr.The compound may include Nd. The compound may include 0.00009 to 0.18at. % oxygen (O). The compound may include 0.028 to 0.1 at. % oxygen(O). The compound may include 0.0001 to 0.09 at. % carbon (C). Thecompound may include 0.0058 to 0.009 at. % carbon (C).

In general, one innovative aspect of the subject matter described inthis specification can be embodied in methods that include the actionsof melting Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb to createa molten alloy, and cooling the molten alloy to create cast alloyflakes. Other embodiments of this aspect include corresponding computersystems, apparatus, and computer programs recorded on one or morecomputer storage devices, each configured to perform the actions of themethods. A system of one or more computers can be configured to performparticular operations or actions by virtue of having software, firmware,hardware, or a combination of them installed on the system that inoperation causes or cause the system to perform the actions. One or morecomputer programs can be configured to perform particular operations oractions by virtue of including instructions that, when executed by dataprocessing apparatus, cause the apparatus to perform the actions.

In general, one innovative aspect of the subject matter described inthis specification can be embodied in methods that include the actionsof melting Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb to createa molten alloy, and fragmenting, using a spray atomizing apparatus, themolten alloy with a high velocity gas jet to create compound dropletsformed from the Cu, Co, Fe and the one or more of Nd, Pr, Dy, or Tb.Other embodiments of this aspect include corresponding computer systems,apparatus, and computer programs recorded on one or more computerstorage devices, each configured to perform the actions of the methods.A system of one or more computers can be configured to performparticular operations or actions by virtue of having software, firmware,hardware, or a combination of them installed on the system that inoperation causes or cause the system to perform the actions. One or morecomputer programs can be configured to perform particular operations oractions by virtue of including instructions that, when executed by dataprocessing apparatus, cause the apparatus to perform the actions.

The foregoing and other embodiments can each optionally include one ormore of the following features, alone or in combination. Melting Cu, Co,and Fe and one or more of Nd, Pr, Dy, or Tb to create the molten alloymay include induction melting Cu, Co, and Fe and one or more of Nd, Pr,Dy, or Tb to create the molten alloy. Melting Cu, Co, and Fe and one ormore of Nd, Pr, Dy, or Tb to create the molten alloy may include arcmelting Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb to createthe molten alloy. Cooling the molten alloy to create the cast alloyflakes may include cooling the molten alloy to create an ingot,re-melting the ingot to make a second molten alloy, and cooling thesecond molten alloy to create the cast alloy flakes.

In some implementations, the method includes agitating the molten alloyusing argon purging to homogeneously distribute the Cu, the Co, and theFe and the one or more of Nd, Pr, Dy, or Tb throughout the molten alloy.Melting Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb to createthe molten alloy may include melting, in an inert atmosphere, Cu, Co,and Fe and one or more of Nd, Pr, Dy, or Tb to create the molten alloy.Melting, in the inert atmosphere, Cu, Co, and Fe and one or more of Nd,Pr, Dy, or Tb to create the molten alloy may include melting Cu, Co, andFe and one or more of Nd, Pr, Dy, or Tb in the inert atmosphere thatincludes a reducing agent. Melting Cu, Co, and Fe and one or more of Nd,Pr, Dy, or Tb to create the molten alloy may include melting, at apressure between 1.5 to 1.8 bar, Cu, Co, and Fe and one or more of Nd,Pr, Dy, or Tb to create the molten alloy.

In some implementations, melting Cu, Co, and Fe and one or more of Nd,Pr, Dy, or Tb to create the molten alloy includes melting Cu, Co, and Feand one or more of Nd, Pr, Dy, or Tb to create the molten alloy usingvacuum induction. Melting Cu, Co, and Fe and one or more of Nd, Pr, Dy,or Tb to create the molten alloy may include melting Cu, Co, and Fe andone or more of Nd, Pr, Dy, or Tb to create the molten alloy at 1450° C.Melting Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb to createthe molten alloy may include melting, in an alumina crucible, Cu, Co,and Fe and one or more of Nd, Pr, Dy, or Tb to create the molten alloy.Melting Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb to createthe molten alloy may include melting, in a zirconium crucible, Cu, Co,and Fe and one or more of Nd, Pr, Dy, or Tb to create the molten alloy.Melting Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb to createthe molten alloy may include melting, in a copper crucible, Cu, Co, andFe and one or more of Nd, Pr, Dy, or Tb to create the molten alloy.

In some implementations, melting Cu, Co, and Fe and one or more of Nd,Pr, Dy, or Tb to create the molten alloy may include melting, in a highdensity crucible, Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb tocreate the molten alloy. Melting Cu, Co, and Fe and one or more of Nd,Pr, Dy, or Tb to create the molten alloy may include melting, in a highpurity crucible, Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb tocreate the molten alloy.

In some implementations, melting Cu, Co, and Fe and one or more of Nd,Pr, Dy, or Tb to create the molten alloy includes melting Nd. MeltingCu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb to create the moltenalloy may include melting Dy. Melting Cu, Co, and Fe and one or more ofNd, Pr, Dy, or Tb to create the molten alloy may include melting Nd andDy. Melting Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb tocreate the molten alloy may include melting Pr. Melting Cu, Co, and Feand one or more of Nd, Pr, Dy, or Tb to create the molten alloy mayinclude melting Tb. Melting Cu, Co, and Fe and one or more of Nd, Pr,Dy, or Tb to create the molten alloy may include melting Pr and Tb.

In some implementations, melting Cu, Co, and Fe and one or more of Nd,Pr, Dy, or Tb to create the molten alloy includes melting, in acrucible, Cu, Co, and Fe and one or more of Nd, Pr, Dy, or Tb to createthe molten alloy, and cooling the molten alloy to create the cast alloyflakes includes cooling the molten alloy in the crucible. Cooling themolten alloy to create the cast alloy flakes may include pouring themolten alloy onto a water cooled wheel to create the cast alloy flakes.Pouring the molten alloy onto the water cooled wheel to create the castalloy flakes may include pouring the molten alloy onto a copper watercooled wheel to create the cast alloy flakes.

In some implementations, cooling the molten alloy to create the castalloy flakes includes cooling the molten alloy at a rate of 105Kelvin/second. Cooling the molten alloy to create the cast alloy flakesmay include cooling the molten alloy at a rate of 10 to 100Kelvin/second. Cooling the molten alloy to create the cast alloy flakesmay include cooling the molten alloy in a vacuum with pressure greaterthan 10-1 bar.

In some implementations, fragmenting, using a spray atomizing apparatus,the molten alloy with a high velocity gas jet to create the compounddroplets formed from the Cu, Co, Fe and the one or more of Nd, Pr, Dy,or Tb includes removing less than about 2 wt. % of the Cu, Co, Fe andthe one or more of Nd, Pr, Dy, or Tb from the molten alloy when creatingthe compound droplets. Fragmenting, using a spray atomizing apparatus,the molten alloy with a high velocity gas jet to create the compounddroplets formed from the Cu, Co, Fe and the one or more of Nd, Pr, Dy,or Tb may include creating the compound droplets with an oxygenconcentration of up to 0.04 wt. %, or less than 0.12 at. %, with acarbon concentration of less than 0.0058 at. %, or both. In someexamples, the compound droplets may include between 0.00009 to 0.18 at.% oxygen, or between 0.028 to 0.1 at. % oxygen. In some examples, thecompound droplets may include between 0.0001 to 0.09 at. % carbon, orbetween 0.0058 to 0.009 at. % carbon. Fragmenting, using a sprayatomizing apparatus, the molten alloy with a high velocity gas jet tocreate the compound droplets formed from the Cu, Co, Fe and the one ormore of Nd, Pr, Dy, or Tb may include fragmenting the molten alloy withan inert gas jet. Fragmenting, using a spray atomizing apparatus, themolten alloy with a high velocity gas jet to create the compounddroplets formed from the Cu, Co, Fe and the one or more of Nd, Pr, Dy,or Tb may include fragmenting the molten alloy with a gas jet with avelocity of 500 m/s.

In some implementations, fragmenting, using a spray atomizing apparatus,the molten alloy with a high velocity gas jet to create the compounddroplets formed from the Cu, Co, Fe and the one or more of Nd, Pr, Dy,or Tb includes fragmenting the molten alloy with a gas jet with apressure of 0.18 to 0.58 MPa. Fragmenting, using a spray atomizingapparatus, the molten alloy with a high velocity gas jet to create thecompound droplets formed from the Cu, Co, Fe and the one or more of Nd,Pr, Dy, or Tb may include creating the compound droplets with an averagediameter of 140 to 180 micrometers. Fragmenting, using a spray atomizingapparatus, the molten alloy with a high velocity gas jet to create thecompound droplets formed from the Cu, Co, Fe and the one or more of Nd,Pr, Dy, or Tb may include creating the compound droplets with a densityof 8.08 g/cm³.

The subject matter described in this specification can be implemented inparticular embodiments and may result in one or more of the followingadvantages. In some implementations, the process has low energyconsumption and low material consumption. In some implementations, GrainBoundary Engineering (GBE) may reduce economic and/or environmentalcosts, without diminishing the magnetic performance and deliverablevalue of a final product, a fully dense Nd—Fe—B sintered magnet. In someimplementations, a GBE Nd—Fe—B magnet product may have an improvedperformance, e.g., high temperature performance, e.g., up to 200° C. Insome implementations, GBE might not have a limitation on the thicknessof a magnet being processed, e.g., and may allow homogeneousdistribution of additive material throughout the whole body of asintered magnet, when compared with other forms of magnet processing. Insome implementations, GBE may control an amount of dopant material,e.g., added to magnetic powder. In some implementations, GBE may allowprecise tailoring of magnetic performance to meet customer requirements.In some implementations, GBE may allow precise addition of additivematerials to a sintered magnet to improve the performance of thesintered magnet while maintaining an original grain phase, e.g., a2:14:1 phase, of the final sintered magnet, e.g., Nd2Fe14B1. Forinstance, the final sintered magnet may not include any of the additivematerial in the grain phase, e.g., the 2:14:1 phase.

In some implementations, the final sintered magnet produced by GBEmodification may have improved material corrosion properties. In someexamples, the GBE modification process has improved processingmethodologies, grain boundary character control, homogeneous mixing,composition and microstructure control, or a combination of two or moreof these, compared to other magnet processing techniques. For instance,the GBE modification process may manipulate the microstructure of theinitial sintered magnet to create a final sintered magnet with improvedmagnetic properties. A GBE system may control the microstructure, forexample grain or domain size, of the final sintered magnet to enhancecorrosion resistance and magnetic performance. The GBE process maycontrol the creation of a new grain boundary, e.g.,Nd11.92Dy42.32Co38.39Cu5.34Fe2.03 at. %, within a grain matrix, e.g., anNd2Fe14B matrix, which may improve corrosion stability of the Nd—Fe—Bsintered or recycled magnet body. In some implementations, a GBE systemcreates final sintered magnets with improved magnetic performance,resistance to inter-granular degradation, improved corrosion resistance,or two or more of these. The GBE system may be used to create finalsintered magnets from recycled magnetic material, only virgin magneticmaterial, e.g., to create the cast alloy flakes and the rare earthtransitional elemental additive material, or a combination of both.

The details of one or more embodiments of the subject matter of thisspecification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-B show an example of a grain boundary engineering process.

FIG. 2 shows an example of a hydrogen mixing reactor.

FIGS. 3A-E show reaction bottles which may be placed on a carriage topermit transport of the reaction bottles into and out of a reactionchamber.

FIGS. 3F-G show an example of another hydrogen mixing reactor with apair of reaction chambers.

FIGS. 3H and 3J show reaction bottles which may be placed on a carriageto permit transport of the reaction bottles into and out of a reactionchamber.

FIG. 3K shows and example of a storage container.

FIG. 4 is a graph that shows an example of property ranges for startingmaterials.

FIG. 5 is a diagram comparing the composition of the original material,shown in the left column, to the finished magnet product, shown in theright column.

FIGS. 6-8 are graphs that show example properties of magnets processedusing Grain Boundary Engineering.

FIG. 9 is an example of a process for applying the Grain BoundaryEngineering technique.

FIG. 10 is an example of a spray atomizing apparatus.

FIG. 11 shows a graph comparing the corrosion resistance of a GBE finalmagnet with other Nd—Fe—B magnets.

FIGS. 12A-B show remanence reversible losses α for starting and finalmagnets.

FIGS. 13A-B show coercivity reversible losses β for starting and finalmagnets.

FIG. 14 shows a graph of example properties of a final magnet.

FIG. 15 shows some examples of magnetic properties of waste sinteredmagnets and recycled magnets.

FIG. 16 shows examples of demagnetization curves of a magnet that hasnot been processed using the GBE process.

FIG. 17 shows examples of demagnetization curves of a magnet that hasbeen processed using the GBE process.

FIG. 18 is a block diagram of a computing system that can be used inconnection with computer-implemented methods described in this document.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

A process may include creation of an N_(d2)Fe₁₄B permanent magnet withspecific performance characteristics, such as desired combinations ofparticle size, alignment, density, energy product (BHmax), remanence(Br), and coercivity (iHc). For instance, a Grain Boundary Engineering(GBE) process may include the production of Nd—Fe—B permanent magnetswith a grain boundary modified rich phase. A GBE process may create newmagnets from new magnetic material, e.g., that has not previously beenused in a consumer product, from recycled magnetic material, e.g., thatwas previously used in a consumer product, or both. The GBE process mayalso be referred to as a Grain Boundary Modification (GBM) process.

As described in more detail below, the GBE process maintains an originalgrain phase of starting magnetic material, while modifying a grainboundary phase of the starting magnetic material. For instance, whencreating a new Nd2Fe14B magnet, a GBE system keeps, from the startingmaterial, at least 90 vol. % of the Nd—Fe—B 2:14:1 phase grains in afinal magnetic product. A GBE system may replace all or substantiallyall of an Nd-rich grain boundary phase with a new grain boundary phasemade from additive material. In some examples, a GBE system maintainsbetween about 90 to about 99.9 vol. % of the starting material, e.g.,2:14:1 phase grains and grain boundary phase, in a final magneticproduct, preferably between about 92 to about 99.75 vol. % of thestarting material is included in the final magnetic product, e.g., 0.25to 8 at. % of the final magnetic product is additive material. In someexamples, the GBE system maintains between about 90 to about 97 vol. %of the starting material. In some examples, a GBE system replacesbetween about 3 to about 12 vol. % of the Nd-rich grain boundary phasewith the new grain boundary phase. For instance, the GBE system mayreplace between 3 to 4.8 vol. % of the Nd-rich grain boundary phase formagnets with a Br between 1.48 to 1.55 T and an iHc between 800 to 1000kA/m, may replace between 6 to 7.2 vol. % of the Nd-rich grain boundaryphase for magnets with a Br between 1.31 to 1.38 T and an iHc between1300 to 1700 kA/m, or may replace between 9 to 12 vol. % of the Nd-richgrain boundary phase for magnets with a Br between 1.18 to 1.26 T and aniHc between 1800 to 2500 kA/m (all values inclusive).

In some implementations, a GBE system may melt alloys and pure elements,e.g., Nd—Pr, Fe—B and Fe, in an argon atmosphere at about 1455° C. Someexample alloys may include the following elements (i) Nd, Pr, Fe, FeB,and B; (ii) Nd, Fe, Co, Cu, and Dy, or (iii) Nd, Fe, Co, Cu, Dy, acomposition with a ratio of Nd 75:Pr 25, a composition with a ratio ofDy 80:Fe 20 and Pr. In some examples, one or more of these elements maybe combined with an alloy of the other elements.

The GBE system pours the molten alloy on a water cooled copper wheelspinning at about 35 rotations per minute (RPM) to form cast alloyflakes. The cast alloy flakes may have a thickness of about 0.2 mm. Thecast alloy flakes may have a grain size ranging from about 5 μm to about80 μm. In some examples, waste magnet material may also be used to formthe cast alloy flakes, e.g., waste magnetic material left over from thecreation of other magnets.

The GBE system pulverizes the cast alloy flakes, e.g., using a jetmilling process, to create fine powders with particles that have a sizebetween about 0.9 μm to about 15 μm. The GBE system presses the finepowders under inert atmosphere at between about 5° C. to about 15° C. ina magnetic field ranging from 400 kA/m to 1200 kA/m to create arectangular compact. The GBE system may apply pressure to the finepowders in a direct perpendicular to the magnetic field. The rectangularcompact may have a length of about 35 mm, a width of about 37 mm, and aheight of about 40 mm.

The GBE system sinters the rectangular compact at about 1070° C. tocreate a sintered compact, e.g., an Nd—Fe—B sintered block. The sinteredcompact, or other sinter Nd—Fe—B magnet compacts, are then processed bythe GBE system using the Grain Boundary Engineering process to modifyonly the rare earth rich phase of the Nd—Fe—B sintered block, e.g., oran Nd—Fe—B magnet. For instance, the GBE system modifies the Nd-richgrain boundary phase of the Nd—Fe—B sintered block.

For example, the GBE system transfers the Nd—Fe—B based sintered blocksto a mixing reactor and places additive material, e.g., Nd—Pr orNd—Dy—Co—Cu—Fe or Nd—Dy, in the mixing reactor.

The GBE system may mix a powder created from the sintered blocks withthe additive material in either inert or hydrogen atmosphere, to name afew examples. When mixing in a hydrogen atmosphere, the GBE system maymix the powder and the additive material for at least 15 hours at 5 RPM.In some examples, as shown in FIG. 1A, the GBE system uses adecrepitation process, e.g., a hydrogen decrepitation process, to createthe fine powders. The GBE system may use any appropriate method toseparate 2:14:1 phase grains 20 in an Nd2Fe14B magnet 10 from an Nd-richgrain boundary phase 30 or, similarly, the phase grains from the grainboundary phase of another type of magnetic material.

In some examples, the mixing may include both coarse and fine mixing.For instance, coarse mixing may create particles from the sintered blockwith an average size of between 1 μm to 2000 mm. The coarse mixing stepmay include evacuating the mixing reactor before admitting hydrogen at apressure of 0.9 bar.

After mixing, the GBE system causes the combined powder, formed from thesintered blocks and the additive material, to absorb hydrogen byexposing the combined powder to hydrogen at room temperature. The GBEsystem then partially degasses the combined powder at 600° C. in situuntil vacuum is restored in the mixing reactor. For instance, duringprocessing, the GBE system may oxidize the Nd-rich grain boundary phaseso that it does not react with the hydrogen. The GBE system may sievethe Nd-rich grain boundary phase material to remove the Nd-rich grainboundary phase material from the Nd—Fe—B grains.

The GBE system then further homogenizes the combined powder using jetmilling to achieve an approximate fine powder particle size of 0.9 to3.5 The GBE system may then sieve the fine combined powder to removelarge oxidized particles. This sieving may remove the Nd-rich grainboundary phase material or may be a separate sieving process.

The GBE system may compact the fine combined powder in inert atmospherebetween 5-15° C. in a magnetic field to form a magnetized green compact.The GBE system may transfer the green compact to a hydraulic chamber andsubject the green compact to an isostatic pressure of 60 MPa. Forinstance, the GBE system may press the green compact in the hydraulicchamber to ensure that a final density of a sintered product, e.g.,after sintering and annealing, is close to theoretical value, e.g.,greater than 4.5 g/cm3. In some examples, the GBE system may compact thefine combined powder in the magnetic field without pressing the greencompact in a hydraulic chamber, e.g., when the density of the magnetizedgreen compact formed in the magnetic field is greater than 4.5 g/cm³.

The GBE system may sinter and anneal the green compact under vacuum,e.g., in a sintering chamber. Once the sintering temperature is reached,Ar partial pressure in the sintering chamber can be adjusted between200-500 mbar, absolute pressure. For instance, introduction of Ar, e.g.,after around twenty minutes at the maximum sintering temperature, mayassist the sintering process to reach the full density of the sinteredbody, e.g., fully dense sintered magnet.

In some implementations, the result of the GBE processing is a fullydense Nd—Fe—B sintered magnet 40 with a modified grain boundary 50,e.g., as shown in FIG. 1B, in which the GBE system may control an amountof doped or additive material in the fully dense sintered magnet. TheGBE process may be a reproducible and precise method for tailoring ofmagnetic performance of sintered magnets, and may provide a significantreduction of heavy rare earth elements, e.g., Dy, Tb, etc., homogeneousdistribution of additive material throughout the whole body of fulldense sintered magnet, e.g., throughout the modified grain boundary 50,and a customized microstructure design, e.g., according to customerrequirements.

The new Nd—Fe—B product 40 may exhibit improved temperature resistance(coercivity, iHc), temperature profile, and corrosion resistance. A GBEmethod may reduce Dysprosium (Dy) material input requirements and lowerbasic operational costs. A GBE process may combine 81-99.9 at. % ofmagnetic material and/or magnet and 0.1-19 at. % of rare earth elementaladditives. A GBE process may have a high affinity for recovery andimprovement of magnetic performance. Some implementations may alleviaterare earth supply risk and end-user vulnerability to rare earth pricevolatility, play an important role in creating a more sustainable magnetsupply chain, or a combination of any two or more of those. In someimplementations, material input requirement costs are reduced byutilizing less Dy material inputs. Resource requirements in terms ofmaterials, waste, pollution, and energy may be reduced with concomitantbenefits.

A method for GBE may employ methods for oxygen suppression. Forinstance, an Nd—Fe—B sintered magnet manufactured using Grain BoundaryEngineering may have an oxygen content of 1.98 at. % or less, or between1.32 at. % and 1.98 at. %, inclusive. Some examples of the atomicpercentage of oxygen content in Nd—Fe—B sintered magnets manufacturedusing Grain Boundary Engineering include 1.00 at. %, 1.10 at. %, 1.32at. %, 1.33 at. %, 1.49 at. %, 1.51 at. %, 1.74 at. %, 1.81 at. %, 1.83at. %, 1.91 at. %, and 1.98 at. %.

A method may include the addition of new rare earth material in a rangeof 0.1 to 19 at. % of the starting material. Further details andoptional features of some implementations include operations thatmaintain, improve, and/or provide specific targeted Nd—Fe—B magnetperformance characteristics. Such performance characteristics mayinclude desired combinations of particle size, alignment, density,energy product (BHmax), remanence (Br), and coercivity (iHc).

In a mixing phase, materials are mixed with additive to achieve desiredfinal properties in a finished product. The mixing process may includecrushing, grinding, milling, or the use of hydrogen to break downmaterials to coarse powder. In some implementations, the magnets, e.g.,Nd—Fe—B or Sm2Co17 type magnets, are processed into a powder using ahydrogen mixing reactor, and the powder material is combined in situwith additives to improve coercivity.

Processes for mixing include milling, cutting, high energy ball milling,roller milling, sawing, jet milling, tumbling, shaking, jaw crushing,and hydrogen mixing. In some implementations, hydrogen mixing is aprocess for homogenizing starting material and fresh rare earthelemental additives. In the hydrogen mixing process, hydrogen enters theΦ phase, e.g., Nd₂Fe₁₄B, and rare earth rich grain boundaries of magnetsand reacts with the rare earth elements forming a hydride with hydrogenbeing trapped in the crystalline structure. The crystal structureexpands as a result of hydrogen absorption and hydride formation causingthe brittle structure to fracture. The result can be effective formixing and, at the same time, for fragmentation of the material andadditive.

The term “fragmentation” as used herein comprehends any type of divisionof solid materials including mechanical, chemical, thermal, radiative,or any suitable process including combinations thereof. The degree offragmentation may be from coarse division to complete disintegration toa fine powder.

In situ production of a desired fine and impurity-free powder mixtureusing hydrogen mixing reactor, together with essential rare earthelemental additives and/or hydride additions of fresh elements, may beeffective for improving magnetic performance from Nd—Fe—B-type sinteredmagnetic materials. Addition of 0.1 wt. %-19 wt. %, preferably 1%, ofadditive elemental additives may be included to improve the magneticperformance and physical properties, e.g., density or corrosionresistance, of the magnetic material. The additions and magneticmaterial may be loaded in the hydrogen mixing reactor to generate acoarse powder mixture of rare earth including Pr₇₅Nd₂₅Hx, where x isranging from 1 to 3 mole fractions.

FIG. 2 shows an example of a hydrogen mixing reactor that breaksmagnetic material, e.g., a sintered magnet, into particles and mixes theparticles. The magnetic material may be waste magnetic material,magnetic material from an end-of-life product, or newly created magneticmaterial, e.g., that has not been used in a consumer product. In someexamples, the magnetic material may be from a newly formed sinteredmagnet created from recycled magnetic material.

In some implementations, the hydrogen mixing reactor mixes elementaladditives with the particles. The hydrogen mixing reactor may createparticles with a target average diameter of between about 1 micron toabout 2 millimeters, or between about 4 to about 7 microns. The hydrogenmixing reactor includes two vessels 102, 104, placed in mixing chambers122, 124 respectively, that each have inner linings 110 that hold themagnetic material and facilitate the circulation of gas around themagnetic material through apertures in the inner linings 110.

The filling of one of the vessels 102, 104 with hydrogen gas while thevessel contains rare earth materials causes the fragmentation of themagnetic material due to hydrogen mixing. Exposure to hydrogen gas canlast for between about 1 to 40 hours. The exposure may be for shorter orlonger periods and the pressure and temperature may be selected based onprocess engineering requirements, other processing stages used toachieve a target particulate size, other processing stages used toachieve a target homogeneous mixture, or any combination of two or moreof these.

Diffusion promotion devices 112, such as snorkels or pipes, withapertures, may be used to ensure that hydrogen mixing causes thebreakdown of the magnets in the reactor vessels 102, 104, and to ensurethat the pile-up of particulate matter does not prevent some of themagnetic material from exposure to the hydrogen gas. Circulationpromoters (not shown) such as stirrers, fans, or gas feeds may helppromote hydrogen gas flow in the vessels 102, 104. Magnetic materialthat falls through the apertures of the inner lining 110 may be stirredby a stirrer located at the bottom of the respective vessel 102, 104.

A removable lid 114 may be provided for the introduction of magneticmaterial into the vessels 102, 104. For example, the magnetic materialmay be placed in the vessels 102, 104 shown in FIG. 2. Magnetic materialmay be transferred into the inner linings 110 by a conveyor or manually,with or without a controlled environment. A small fraction of rare earthtransitional elemental additive material may be added to the innerlinings 110 to bring the properties of a final product made from themagnets to a predefined specification remanence, energy product, and/orcoercivity. In some examples, an additive may be added to crushedmagnetic material after mixing to adjust the properties of the finalproduct. Some examples of the additive material may include Nd, Pr, Dy,Gd, Tb, La, Ce, Yb, Ho, or Eu, or combinations of two or more of these.

The vessels 102, 104 may withstand a predefined pressure. For instance,the hydrogen mixing reactor may include a vacuum pump. In someimplementations, the pressure may be increased up to 60 bar. The vessels102, 104 may also withstand lower pressures. The vessels 102, 104 mayhave thermostatically controlled heaters 116 and pressure regulationcontrols.

The hydrogen mixing reactor includes gas source connections 138 thatintroduce hydrogen or other gases into the vessels 102, 104 through apumping assembly 128 and a valve assembly 133. The pumping assembly 128,the valve assembly 133 a gas management component 144, or a combinationof two or more of these, may feed gas directly into the diffusionpromotion devices 112, to ensure full volumetric perfusion of themagnetic material in the vessels 102, 104. In some examples, the pumpingassembly 128 and the valve assembly 133 may connect the vessels 102,104, allowing for vacuum pump evacuation of the vessels 102, 104, e.g.,for degassing or primary loading of gas, pumping gas from one vessel tothe other, e.g., to reclaim hydrogen gas, venting to atmosphere, e.g.,using ambient connections 132 to the external atmosphere, pressurizingthe vessels 102, 104, backfilling one or both of the vessels 102, 104with inert gas, performing other reclamation processes or combinationsof two or more of these. A controller 140 may be connected to the valveassembly 133 and the pump assembly 128 to automate the hydrogen mixingprocesses and hydrogen transfer between the vessels 102, 104.

During the hydrogen mixing process, magnetic particles fall from thevessels 102, 104 through chutes 126 into a chamber 120. The magneticparticles may be removed from the chamber 120 for further processing. Insome implementations, press-withstanding valves may be employed at theopenings between the chutes 126 and the vessels 102, 104.

In some implementations, one of the vessels 102, 104 is made gas tightand evacuated using the gas management component 144. The selectedvessel 102, 104 may then be filled with hydrogen from a gas source,e.g., through the pumping assembly 128, to prepare the selected vessel102, 104 for mixing and fragmentation of magnetic material. After mixingand fragmentation, the hydrogen may be transferred by the gas managementcomponent 144 to the other vessel 104, 102, e.g., by evacuating thehydrogen from the selected vessel 102, 104 and transferring the hydrogento the other vessel 104, 102. As each vessel's contents are subjected tohydrogen mixing, the hydrogen can be recovered and transferred to theother vessel 102, 104 and the process of hydrogen mixing is repeated inthe other vessel.

In some implementations, a gas storage chamber is included in the gasmanagement component 144 and the hydrogen evacuated from one of thevessels 102, 104 is temporarily stored in the gas storage chamber (notshown) prior to transfer to the other vessel 102, 104, e.g., betweenhydrogen mixing cycles. The use of the gas storage chamber may allow thehydrogen mixing reactor to include only one vessel. In some examples,the hydrogen mixing reactor may include more than two vessels. The gasstorage chamber may include multiple chambers constituting respectivestages with volumes chosen to maximize the energy economy for transferof gas to and from the chambers and the vessels 102, 104 by minimizingthe pressure drop or elevation during transfer.

FIG. 3A shows a set of four reaction bottles 212 on a carriage 216,which transports the reaction bottles 212 into and out of a reactionchamber, e.g., one of the reaction chambers 202, 202′ shown in FIG. 3F.The reaction chambers 202, 202′ may be used in conjunction with orinstead of the hydrogen mixing reactor shown in FIG. 2. In someexamples, the reaction bottles 212 may be used with the hydrogen mixingreactor shown in FIG. 2, e.g., as the vessels 102, 104. For example, thegas management component 144 may fill the bottles 212 with inert gas,e.g., Ar or N, that are subsequently filled with magnetic material,e.g., newly sintered magnets. Magnetic material 206 such as magnets,e.g., to be hydrogenated, may be loaded from a transfer chute 208 intothe reaction bottles 212. The magnetic material 206 may be loaded intothe reaction bottles 212 in an inert atmosphere, to prevent thecontamination of the magnetic material 206 such as by oxygen.

In some implementations, a small fraction of rare earth transitionalelemental additive material may be added to the reaction bottles 212.The rare earth transitional elemental additive material may be selectedto bring the properties of a final product, produced from the magneticmaterial 206 and the rare earth transitional elemental additivematerial, to a predefined specification remanence, energy product, andcoercivity. In some examples, a hydride of the rare earth transitionalelemental additive material may be added to the hydrogenated magneticmaterial 206 after mixing and fragmentation of the material in thereaction chambers 202, 202′.

Each of the reaction bottles 212 may include a snorkel 213 or anotherdevice that facilitates gas diffusion in the reaction bottles. Forexample, the snorkels 213 may be a cylinder with openings in the sidethat allow for the diffusion of gas, so the gas reaches magneticmaterial positioned in the center of each bottle 212.

The bottles 212 and the snorkels 213 may be open at the top to allowhydrogen gas to enter the bottles 212 and the snorkels 213 and contactthe magnetic material 206 contained within the bottles 212 and/or toallow loading of the magnetic material 206 into the bottles 212.

When the magnetic material 215, e.g., magnets, is positioned within thebottles 212, shown in FIG. 3B, a transfer cover 214 may be attached tothe carriage 216 to isolate the bottles 212 and their contents fromexternal atmosphere. The container formed by the cover 214 and carriage216 may preclude gas leakage so that its internal volume can maintain anatmosphere of inert gas preventing ambient air from contacting themagnetic material 215. For instance, after the bottles 212 are loadedwith the magnetic material 215 in the inert atmosphere, the bottles 212may be covered by the cover 214, and the carriages 216 stored outsidethe space with the inert atmosphere. For instance, FIG. 3E shows anexample of a loaded bottle 212 prior to the placement of the loadedbottle 212 onto the carriage 216 and the cover 214 on top of the loadedbottle 212. The bottles 212 may be loaded while on the carriage 216 ormay be loaded and then placed onto the carriage 216.

FIGS. 3F-G show an example of another hydrogen mixing reactor with apair of reaction chambers 202, 202′. The reaction chambers 202, 202′ areconnected to, and interconnected by, a gas management component 144 asdiscussed above. The gas source 138 may provide respective connectionsfor multiple gases such as inert gas and hydrogen. The ambientconnection 132 may provide a vent to atmosphere. The gas managementcomponent 144 operates as described above with reference to FIG. 2 inthat it transfers gas from one reaction chamber 202 to the other 202′and vice versa, instead of between the vessels 102, 104.

A covered carriage 260, e.g., the carriage 216, is rolled into a firstone of the reaction chambers 202 while hydrogenation is occurring in theother reaction chamber 202′, e.g., for bottles placed on anothercarriage in the other reaction chamber 202′. Once the covered carriage260 is in the reaction chamber 202, the cover 214 is removed from thecarriage 260 and a hatch 252 on the reaction chamber 202 is closed. Thereaction chamber 202 may then be filled with inert gas, e.g.,transferred from the other reaction chamber 202′ after processing in theother reaction chamber 202′ is complete.

The gas management component 144 may supply, to the reaction chamber202, hydrogen from a hydrogen source to achieve a required pressure. Forinstance, when the hydrogenation in the reaction chamber 202′ iscomplete, the gas management component 144 transfers hydrogen from thereaction chamber 202′ into the reaction chamber 202 and pressurizes thereaction chamber 202 to a target pressure. The gas management component144 may initiate hydrogenation in the reaction chamber 202 byintroducing the hydrogen gas, e.g., pressurized hydrogen gas, from thereaction chamber 202 into the bottles 212 through the covers 232 orother openings in the bottles.

The hydrogen mixing process may create magnetic particles with anaverage diameter of between about 1 micron to about 2 mm, e.g., when thehydrogen mixing reactor performs an initial mixing process, or betweenabout 4 microns to about 7 microns, e.g., when the hydrogen mixingreactor performs a second mixing process. In some examples, the hydrogenmixing reactor shown in FIGS. 3F-G may perform both processes, thehydrogen mixing reactor shown in FIG. 2 may perform both processes, orone of the reactors may perform one process and the other reactor mayperform the other process. For instance, the hydrogen mixing reactorshown in FIG. 2 may perform the first mixing process and the hydrogenmixing reactor shown in FIGS. 3F-G may perform the second mixingprocess.

The gas management component 144 may evacuate, e.g., completely, gasfrom the reaction chamber 202′ and place the gas in the reaction chamber202, for use during processing in the reaction chamber 202, or in astorage chamber or vessel. A thermostatically regulated heater 257within the reaction chamber 202, shown in FIG. 3G, may be regulated by acontroller to provide a target temperature.

As the hydrogenation process proceeds in the reaction chamber 202, thegas management component 144 backfills the reaction chamber 202′ withinert gas. The hatch 252′ to the reaction chamber 202′ is then opened,as shown in FIG. 3G, and a cover 214′ is placed on the carriage 260′.The hydride magnet material, now reduced to particles, then moves outfrom the reaction chamber 202′ in the carriage 260′.

After the hydrogenation is completed in the reaction chamber 202, thegas management component 144 evacuates the excess hydrogen gas from thereaction chamber 202. For instance, the hydrogenation process may beginagain for one or more bottles 212 placed in the reaction chamber 202′and transfer the excess hydrogen gas, e.g., and leave some hydrogenmaterial in the magnetic material that was processed, to the reactionchamber 202′ from the reaction chamber 202.

In some implementations, the bottles 212 can be closed with a cover 232,shown in FIGS. 3C-D and 3J, that acts as a funnel to permit recoveredhydride magnet particles to be directed through a chute 237 when a valve234 is open, e.g., when the bottle 212 is in the inverted position. Thecover 232 may be removed, e.g., to allow the magnetic material 206 toenter the bottles 212, and placed on the respective bottles 212afterward.

Referring to FIG. 3J, in an inert atmosphere, the covers 232 arepositioned on the bottles 212 and the bottles can be sealed and removedfrom the inert atmosphere without the need for the cover 214. Thebottles 212 can be transported by the carriage 216 or individually.

FIG. 3K shows and example of a storage container 240 for the magneticparticles received from the bottles 212. The valves 234 on the bottles212 accept a nozzle 265, included in the storage container 240, to seala manifold 267 to the snorkels 213 in the bottles 212. A blower 266feeds inert gas through the manifold 267 and into the snorkels 213 toremove magnetic particles from the bottles 212 into the storagecontainer 240. The inert gas may circulate back into the storage chamber240 after entering one of the bottles 212.

The inert gas may flow out of the snorkels 213 in a tangential or radial(or both) flow, as shown in FIG. 311 which is a cross section of abottle 212 and a snorkel 213. The arrows show the tangential pattern ofthe inert gas ejected through tangentially-aimed slots in the snorkel213. The tangential pattern of the inert gas flow may help removeparticles from the inside walls of the bottle 212 and facilitate fullyemptying the magnetic particles from the bottles 212.

The valve 234 may have a gate configuration, e.g., to permit the entryof the nozzle 265 into the bottle 212. A cover 268 may be place on thenozzle 265 to seal the storage container 240 when the bottles 212 areremoved.

FIG. 4 is a graph that shows an example of property ranges for startingmaterials, e.g., recycled magnets from a variety of different types ofconsumer products and that include a variety of different magneticproperties. A bubble 302 drawn onto the graph represents the approximaterange of starting materials to which the process can apply. The processmay also apply to other starting materials outside of the bubble 302.

FIG. 5 is a diagram comparing the composition of the original magneticmaterial, shown in the left column, to the finished magnet product,shown in the right column, created by the process. In the startingmaterial, the composition of rare earth metals may be greater or lessthan 18 at. %, noted by the “R” region of the left column. The rareearth metals may be included in the grains of the original magneticmaterial or in the grain boundary phase material. An amount of rareearth metals “X” is removed from the starting magnet material duringprocessing, e.g., from the grain boundary phase material. For instance,a GBE system may remove substantially all of an Nd-rich grain boundaryphase from the original magnetic material. In order for the finalNd—Fe—B product to have a composition similar to the original magnet,new rare earth material, i.e., virgin material, must be added. The newrare earth material, e.g., the additive material, may replace theNd-rich grain boundary phase removed from the original magneticmaterial.

In FIG. 5, the virgin material is represented by the “V” region and isapproximately equal to the amount of rare earth metals removed duringprocessing, or “X.” In the finished product, the final percentage ofrare earth metals is at least the percentage in the starting magneticmaterial, but not higher than 18 at. %. If the percentage of rare earthmaterial in the starting magnetic material “R” is as low as the lower ofthe two dashed lines in the left column, e.g., less than 18 at. %, thefinal rare earth atomic percentage in the finished magnet product, sownin the right column, is at least equal to the same percentage, asdepicted by the lower dashed line carrying over. If, however, thepercentage of rare earth metals in the starting material is greater than18 at. %, then the atomic percentage in the finished magnet is limitedto 18%, as shown by the upper dashed line being capped at 18% in theright column.

In the finished product, the final rare earth atomic percentage is onein which the percentage of each component, Nd, Pr, Dy, Gd, Tb, La, Ce,Yb, Ho, and/or Eu of virgin material is in the range of 0.1 to 19 at. %of its percentage in the original material, and the atomic percentage ofNd or Pr or both is greater than zero. The following formulas furtherdescribe some implementations: R=s(Nd) s(Pr) s(Dy) in the staring magnetmaterial; T=f(Nd)+f(Pr) f(Dy) in final Nd—Fe—B product, as defined inparagraph 19; and virgin material added V=Nd[p]Pr[q]Dy[r], where0.1≤p+q+r≤19 at. % of final product and T≥min(R, 18 at. %). Forillustrative purposes, consider the following example: If the atomicpercentage values for Nd, Pr, and Dy in an starting magnet material are9.77, 2.96, and 0.92, respectively, then substituting the correspondingvalues into the formula R=s(Nd) s(Pr) s(Dy) yields R=9.77 2.96+0.92, orR=13.65. In the same example, the atomic percentage values for Nd, Pr,and Dy in the new Nd—Fe—B sintered magnet might be 10.74, 3.26, and0.91, respectively. Upon substituting the values of the new Nd—Fe—Bsintered magnet into the formula T=s(Nd) s(Pr) s(Dy), T then equals10.74+3.26+0.91, or T=14.91. If, in the same example, virgin material isadded during the GBE process, and the virgin material contains atomicpercentage values of 0.2, 0.3, and 0.4 for Nd, Pr, and Dy, respectively,the formula V=Nd[p]Pr[q]Dy[r] yields V=0.2+0.3+0.4, or V=0.9. Theformula for the virgin material, or V, is subject to two constraints:0.1≤p+q+r≤19 at. % of final product and T≥min(R, 18 at. %). In ourexample, p q r=0.9 at. %, which satisfies the first constraint—that thevalue of p q r must be greater than or equal to 0.1 at. % and less thanor equal to 19 at. %. This example also satisfies the second constraintfor the formula for the virgin material: T is greater than or equal tothe minimum of the set of R or 18. In this example, T is 14.91 and theminimum of the set of R or 18 is R, which is 13.65, so T is greater thanor equal to the minimum of the set of R or 18.

In some implementations, V=Nd[p]Pr[q]Dy[r], where 0.1≤p+q+r≤15 at. % offinal product and T≥min(R, 18 at. %). In some implementations,V=Nd[p]Pr[q]Dy[r], where 0.1≤p+q+r≤12 at. % of final product andT≥min(R, 18 at. %). In some implementations, V=Nd[p]Pr[q]Dy[r], where0.1≤p+q+r≤8 at. % of final product and T≥min(R, 18 at. %). In someimplementations, V=Nd[p]Pr[q]Dy[r], where 0.1≤p+q+r≤5 at. % of finalproduct and T≥min(R, 18 at. %). In some implementations,V=Nd[p]Pr[q]Dy[r], where 0.1≤p+q+r≤3 at. % of final product and T≥min(R,18 at. %). In some implementations, V=Nd[p]Pr[q]Dy[r], where 0.1≤p+q+r≤2at. % of final product and T≥min(R, 18 at. %). In some implementations,V=Nd[p]Pr[q]Dy[r], where 0.1≤p+q+r≤1 at. % of final product and T≥min(R,18 at. %).

In some implementations, X is at. % RE (Nd, Pr, Dy) removed fromoriginal magnet, and p+q+r≥X. In some implementations, the additive issuch that in the final Nd—Fe—B sintered product, where f is a fractionby at. % of starting Nd—Fe—B sintered magnetic material, f(Nd)+f(Pr)>0.In some implementations, f(Nd)+f(Pr)+f(Dy)≤18. In some implementations,f(Co)≤3. In some implementations, f(Cu)≤0.3. In some implementations,f(Fe)+f(Co)≤77. In some implementations, f(Dy)+f(Nd)+f(Pr)≥R.

In some implementations, the elemental additions are Nd[0.1-19 at.%*s(Nd), x]Pr[0.1-19 at. %*s(Pr), y]Dy[0.1-19 at. %*s(Dy), z]Co[0,d]Cu[0, e]Fe[0, f], where [m, n] means a range from minimum m andmaximum n; s(t) is the atomic percent of element t in startingcomposition; f(t) is the atomic percent of element t in finalcomposition; x=18−[81, 99.9] at. %*(s(Nd)+s(Pr)+s(Dy)); y=18−[81, 99.9]at. %*(s(Nd)+s(Pr)+s(Dy)); z=18−[81, 99.9] at. %*(s(Nd)+s(Pr)+s(Dy));d=3−[81, 99.9] at. %*s(Co); e=0.3−[81, 99.9] at. %*s(Cu); f=77−[81,99.9] at. %*(s(Fe)+s(Co)).

In some implementations, (i) virgin material, e.g., NdpPrqDyr, need bein the range of 0.1≤p+q+r≤19 at. % of final product, and T≥min(R, 18),where T=f(Nd)+f(Pr)+f(Dy) and R=s(Nd)+s(Pr)+s(Dy); (ii) p+q+r≥X, where Xis at. % RE (Nd, Pr, Dy) removed from original magnet; (iii) T≤18 at. %;(iv) f(Nd)+f(Pr)>0, where f is an at. % fraction of the final product;(v) f(Nd)+f(Pr)+f(Dy)<=18; (vi) f(Co)<=3; (vii) f(Cu)<=0.3; (viii)f(Fe)+f(Co)<=77; and (ix) f(Dy)+f(Nd)+f(Pr)>=R.

Besides the rare earth metals, the remainder of both the startingmagnetic material and finished magnets may include of Fe, Co, Cu, Al,and other elements. In some examples, other types of magnetic materialmay be used. Final magnet products made with other types of magneticmaterial may have different compositions of magnetic material.

The following examples demonstrate that starting magnet material may beprocessed according to the Grain Boundary Engineering technique toproduce a final Nd—Fe—B magnet with maintained or minimal loss ofcertain magnetic properties including remanence (Br); and improvement ofother properties including temperature resistance (iHc) and temperatureprofile, while more efficiently using and optimization content ofDysprosium (Dy) in the Nd—Fe—B final product, which may reduce cost andsupply vulnerability. In some implementations, the method is not limitedby the thickness of the magnetic body. For instance, the use of the rareearth transitional elemental additive material, e.g.,Nd₁₋₂₀Dy₁₋₆₀Co₁₋₆₀Cu_(0.1-20)Fe_(0.5-90) at. %,Nd₇₋₁₄Dy₃₀₋₅₀Co₂₈₋₄₅Cu₁₋₁₀Fe₁₋₁₀ at. %,Nd_(8.5-12.5)Dy₃₅₋₄₅Co₃₂₋₄₁Cu_(3-6.5)Fe_(1.5-5) at. %, orNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. %; for the grainboundary phase of the Nd—Fe—B final product may allow the Nd—Fe—B finalproduct to be any thickness, e.g., greater than 6 millimeters thick.

Example 1

These examples demonstrate that the overall magnetic performance ofpermanent magnets can be improved, with minimum amount of dopants usingthe GBE process. For instance, the GBE process may result in 27%increase in coercivity and 0% decrease in remanence as shown in FIG. 6,or 83% increase in coercivity and 6% decrease in remanence as shown inFIG. 7, or 60% increase in coercivity and 3% decrease in remanence asshown in FIG. 8. For instance, FIG. 6 shows an example of variations ofNd—Fe—B-type sintered magnets with 0.5 at. % additions, e.g., Nd or Dy,resulting in high energy. The final magnet with 0.5 at. % additions hasa remanence (Br) of 1.423 T, a coercivity (iHc) of 1042 kA/m and anenergy product (BHmax) of 391 kJ/m³. FIG. 7 shows an example ofvariations of Nd—Fe—B-type sintered magnets with 3 at. % additions,e.g., Dy, resulting in high coercivity suitable for high temperatureapplications. The final magnet with 3 at. % additions has a remanence(Br) of 1.29 T, a coercivity (iHc) of 1900 kA/m and an energy product(BHmax) of 323 kJ/m³. The densities of both magnets are 7.56 g/cm³.

In one example, a magnet with the properties shown in FIG. 6 may include0.5 at. % Nd dopant. The starting material of the magnet may have acomposition shown in Table 1 below, identified as “Starting Material,”before the addition of the Nd dopant and a final composition, identifiedas “Final Material,” after the addition of the Nd dopant. In someexamples, this magnet may have high energy.

TABLE 1 0.5 atom % Nd dopant Nd Pr Dy B Al Fe C O Stage (at. %) (at. %)(at. %) (at. %) (at. %) (a. %) (at.m %) (at. %) Starting Material 10.503.04 0.12 6.92 0.52 Balance 0.31 0.95 Final Material 11.39 3.01 0.376.85 0.52 Balance 0.31 1.00

In one example, a magnet with the properties shown in FIG. 7 may include3 at. % Dy dopant. The starting material of the magnet may have acomposition shown in Table 2 below, identified as “Starting Material,”before the addition of the Dy dopant and a final composition, identifiedas “Final Material,” after the addition of the Dy dopant. In someexamples, this magnet may have high coercivity.

TABLE 2 3 atom % Dy dopant Nd Pr Dy B Al Fe C O Stage (at. %) (at. %)(at. %) (at. %) (at. %) (a. %) (at.m %) (at. %) Starting Material 9.973.18 0.17 5.81 0.75 Balance 0.37 0.22 Final Material 9.80 2.98 1.37 5.620.76 Balance 0.62 0.53

In some examples, the composition of the magnets identified in Tables 1and 2 may have an accuracy between about 0.009 to about 0.08 at. %. Insome examples, the magnets identified in Tables 1 and 2 may includeother minor dopants.

Grain Boundary Engineering might not be limited to a thickness of about6 mm of the magnet sintered body. For instance, a system may performGrain Boundary Engineering to form sintered magnets that are more thanabout 6 mm thick or more than 6 mm thick. In some examples, thethickness of magnets formed using the Grain Boundary Engineering processare 6 mm thick or more.

FIG. 8 shows an example of demagnetization curves of GBE-processedsintered magnets containing different amounts of Dy additions to Nd—Fe—Btype sintered magnets. For instance, the GBE technique described hereinmay be applied to sintered magnets on a mass scale to improve remanenceand coercivity by adding 0.5 at. % additive material, 2.0 at. % additivematerial, or 3.0 at. % additive material to achieve the respectiveproperties shown in FIG. 8.

FIG. 9 is an example of a process 900 for applying the Grain BoundaryEngineering technique. The process 900 may be performed using one ormore of the systems described above.

At 902, the process forms cast alloy flakes. For instance, a GBE systemmelts an alloy, pure elements, or both, and pours the molten alloy on awater cooled copper wheel to form the cast alloy flakes. The cast alloyflakes include multiple 2:14:1 phase grains, e.g., of Nd2Fe14B1. In someexamples, each of the cast alloy flakes include 2:14:1 phase grains. Insome examples, some of the cast alloy flakes include 2:14:1 phase grainsand some of the cast alloy flakes include a) grains that include othermaterials, e.g., materials other than Nd, Fe, or B such as contaminants,or b) grains that include different compositions of Nd—Fe—B, e.g., otherthan N_(d2)Fe₁₄B₁.

The combinations of elements used in the alloy, separately as pureelements, or in a combination of an alloy and pure elements, mayinclude: (i) Nd, Pr, Fe, FeB, and B; (ii) Nd, Fe, Co, Cu, and Dy, (iii)Nd, Fe, Co, Cu, Dy, a composition with a ratio Nd₇₅:Pr₂₅, a compositionwith a ratio Dy₈₀:Fe₂₀ and Pr, (iv) Nd₂Fe₁₄B, (v) D_(y2)Fe₁₄B, (vi)Pr₂Fe₁₄B, (vii) Tb₂Fe₁₄B, (viii) Nd₂Co₁₄B, (ix) Pr₂Co₁₄B, (x) Tb₂Co₁₄B,(xi) Nd₂Ni₁₄B, (xii) Pr₂Ni₁₄B, (xiii) Tb₂Ni₁₄B, (xiv) V₂FeB₂, (xv)NbFeB, (xvi) MoFeB, (xvii) ZrFeB, (xviii) TiFeB, (xix) Nd-rich, (xx)CoNd₃, (xxi) NiNd₃, (xxii) GaNd, (xxiii) Nd-oxide, (xxiv) Proxide, (xxv)RE-Carbide, (xxvi) Nd-Oxifluoride, (xxvii) Re-Nitride, or (xxviii) acombination of two or more of these. In some implementations, some orall of the elements may be from waste magnet material. In someimplementations, some or all of the elements are from new magneticmaterial, e.g., that has not been previously used in a consumer product.

At 904, the process pulverizes the cast alloy flakes to create aninitial powder. For instance, the GBE system may use a jet millingsystem, or another appropriate system, e.g., high speed energy millingunder Ar or He or another inert gas, to create the initial powder fromthe cast alloy flakes. In some implementations, the GBE system mayexpose the cast alloy flakes to hydrogen gas at a temperature betweenabout 20 to about 150° C. and a pressure of up to about 1 to about 10bar to decrepitate the cast alloy flakes. The GBE system maintains the2:14:1 phase grains, or between about 90 to 97 vol. % of those grains,when creating the initial powder.

At 906, the process aligns and presses the initial powder to create aninitial compact. For example, the GBE system creates a pressed compactfrom the initial powder.

In some implementations, some boron from the starting elements may belost during processing of the alloy, e.g., during preparation andforming of the cast alloy flakes, creation of the initial powder,creation of the initial compact, or two or more of these. In someimplementations, oxygen, carbon, or both, may be mixed with the powderduring the processing of the alloy. For instance, the alloy mayinitially be Nd14.2Fe79.3B6.5 (at. %) and the initial compact may beNd14.2Fe79.55B6.1C0.05O0.1 (at. %). In some examples, the alloy mayinitially be Nd31.284Fe67.6427B1.0733 (wt. %) and the initial compactmay be Nd_(31.2275)Fe_(67.7335)B_(1.0054)C_(0.0092)O_(0.0244) (Wt. %).

At 908, the process sinters the initial compact. For example, the GBEsystem creates a fully dense sintered magnet from the initial compact.In some implementations, oxygen, carbon, or both may be added to theinitial compact during sintering. For instance, the GBE system may add alubricant to the initial compact during or as part of a sinteringprocess and oxygen, carbon, or both may be added to the initial compactas a result of the lubrication. In some examples, a sintering processmay include the use of argon gas and oxygen present in the argon gas maybe added to the initial compact, e.g., during sintering.

The GBE system may perform steps 902 through 908 to create a sinteredmagnet with multiple 2:14:1 phase grains and then process the sinteredmagnet using steps 910 through 918, described below, to maintain the2:14:1 phase grains of the sintered magnet in a final product. Forinstance, the process 900 may maintain all or between about 90 to 97vol. % of the 2:14:1 phase grains created in the cast alloy flakes inthe fully dense sintered magnet, made in step 908, and maintain all orbetween about 90 and 97 vol. % of the 2:14:1 grains from the fully densesintered magnet in the powder created in step 910, described in moredetail below.

In some examples, the GBE system receives a new magnet, e.g., that hasnot been used in a commercial process, or a magnet which hasn't beenused much, and processes that magnet instead of performing steps 902through 908. The GBE system may use any appropriate type of sinteredmagnet instead of performing steps 902 through 908.

At 910, the process places the magnetic material in a mixing apparatusto create a powder. The mixing apparatus may subject the magneticmaterial to a pressurized hydrogen atmosphere for a predetermined periodof time, temperature, rotational speed, etc. For instance, the magneticmaterial may be processed by the hydrogen mixing reactor shown in FIG.2, FIG. 3G, or both or another appropriate mixing apparatus. The GBEsystem, e.g., the mixing apparatus, maintains all or between about 90and 97 vol. % all of the 2:14:1 phase grains from the magnetic materialwhen creating the powder. In some implementations, when the GBE systemcreates a powder from the initial sintered magnet, the GBE systemremoves an old Nd-rich grain boundary phase from the initial sinteredmagnet.

In some examples, rare earth transitional elemental additive materialmay be added to the magnetic material before or after mixing. In someimplementations, Nd—Fe—B magnets, e.g., magnetic material and rare earthelemental additive, for example, Nd_(1-x)Pr_(x), are placed together ina mixing apparatus at a ratio between 99.9:0.1 to 81:19 at. % and arehomogeneously blended together, e.g., in-situ. In some examples, a ratiobetween 99.9:0.1 to 94:6 at. %, magnetic material to rare earthtransitional elemental additive material, specifically a ratio between99.9:0.1 to 99:1 at. %, are homogeneously blended together. The rareearth transitional elemental additive material may be fragmentedseparately and added to the magnetic material after step 910.

For instance, the GBE system may mix a rare earth transitional elementaladditive of Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % withthe Nd₂Fe₁₄B powders to produce composite powders and, optionally,replace the old Nd-rich grain boundary phase, which is normally presentin the sintered Nd—Fe—B-type magnet body, with theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % material. In someexamples, the GBE system may use flash pyrolysis ofNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % fine powder toform a precursor and mix the precursor with Nd₂Fe₁₄B powders to create acomposite powder. The GBE system may use a hydrogen mixing reactor for afirst mixing step, e.g., that disperses fineNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % articles into anNd₂Fe₁₄B powder.

In some implementations, the GBE system may create theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % rare earthtransitional elemental additive material, e.g., the precursor, using arcmelting, RF (radio frequency), book molding, strip casting or atomizingor any other appropriate method to prepare optimum composition of thefinal precursor. In some examples, the purity level of the elements inthe precursor, e.g., Nd, Dy, Co, Cu and Fe, is 95% or higher, e.g.,99.9% purity, to produce theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % rare earthtransitional elemental additive material.

In some examples, a GBE system may use a melting preparation process,e.g., vacuum induction melting, to prepare the rare earth transitionalelemental additive material. For instance, the GBE system may use vacuuminduction melting preparation of a multicomponent, highly alloyedmaterial that includes at least copper, cobalt, iron and one or moremodifier elements, e.g., neodymium, praseodymium, dysprosium, terbiumand combinations of two or more of these. The GBE system may use thealloyed material to replace the Nd-rich grain boundary phase present inthe sintered magnets.

For instance, the GBE system may melt the elements of the alloy, e.g.,Nd, Pr, Fe, Dy, Tb, Co, Cu, elements in the alumina or zirconiumcrucible, e.g., a high density crucible, a high purity crucible, orboth, to prepare a compound of the elements, e.g., of five elements.Some examples of the compound may include Nd₂Dy₇Co₆CuFe_(0.33),Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. %,Pr_(11.92)Tb_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. %, orPr₂Tb₇Co₆CuFe_(0.33), e.g., see Tables 3 and 4. For example, the Ndelement can be substituted by Pr and the Dy element can be substitutedby Tb.

The GBE system melts the elements at 1450° C. to create a molten alloyand pours the molten alloy material from the alumina or zirconiacrucible onto a water cooled copper wheel to create cast alloy flakes.In some examples, the GBE system may cool the molten alloy in thecrucible to room temperature to create a block from the compound. TheGBE system may rapidly cool the molten alloy to create strip castedalloy flakes, e.g., at a rate of 105 Kelvin/second, e.g., to achieveflakes less than 50 micrometers in size. In examples when the GBE systemslowly cools the molten alloy, the GBE system may cool the molten alloyat a rate between 10 to 100 Kelvin/second.

The GBE system may melt the elements in Ar atmosphere, e.g., atapproximately 1.5 bar absolute pressure, or another inert gas, e.g.nitrogen. In some examples, the GBE system may melt the elements invacuum allows. For instance, when the GBE system uses an inert gas orvacuum during melting and creation of the compound, e.g., for the rareearth transitional elemental additive material alloy, the GBE system mayslightly increase the oxygen content, the carbon content, or both, inthe alloy. In some examples, when the GBE system uses an inert gas orvacuum during melting and creation of the compound, the GBE system maysuppress loss of neodymium, dysprosium, praseodymium, or two or more ofthese, e.g., due to the evaporation.

In some implementations, the GBE system may use an induction meltingprocess of at least 400 V, 3000 Hz and 100 KW power, for a charge sizeof 55 Kg. The GBE system may include operative amounts of a reducingagent in the inert atmosphere used during melting of the elements. Forinstance, the GBE system may use hydrogen as a reducing agent. In someexamples, the GBE system may agitate the elements in the crucible byargon purging through the bottom of a porous crucible to achievehomogeneous distribution of the elements in the melt.

The GBE system may reduce the amount of 0, C, or both, introduced intothe rare earth transitional elemental additive material by preparing thecompound as described above, e.g., compared to other techniques foralloy preparation. The GBE system may replace part or all of an Nd-richgrain boundary phase with a liquid eutectic phase of the alloy toincrease the properties of a final sintered magnet body.

TABLE 3 Nd₂Dy₇Co₆CuFe_(0.33) Alloy Properties Average Oxygen CarbonOxygen Content Content and Carbon Elemental Elemental in Elemental inElemental Introduced Content Material Material Material into Alloy inAlloy Nd 0.08 wt % Below 13.44 detection limit Dy 0.03 wt % Below 61.50detection limit Co Below 0.005 wt % 19.280 detection limit Cu BelowBelow 3.130 detection detection limit limit Fe Below Below 2.466detection detection limit limit Oxygen — —  0.06 wt % 0.17 wt % Carbon —— 0.009 wt % 0.014 wt %  Total — — —  100 wt %

TABLE 4 Pr₂Tb₇Co₆CuFe_(0.33) Alloy Properties Average Oxygen CarbonOxygen Content Content and Carbon Elemental Elemental in Elemental inElemental Introduced Content in Material Material Material into AlloyAlloy Nd 0.07 wt % Below 14.100 detection limit Dy 0.02 wt % Below61.400 detection limit Co Below 0.004 wt % 19.500 detection limit CuBelow Below 3.100 detection detection limit limit Fe Below Below 2.466detection detection limit limit Oxygen — —  0.03 wt % 0.12 wt % Carbon —— 0.006 wt % 0.01 wt % Total — — —  100 wt %

In some implementations, the GBE system may use an arc melting process,e.g., vacuum melting or re-melting, to prepare the rare earthtransitional elemental additive material. For instance, the GBE systemmelts the elements for the alloy, e.g., the elements described above, ina copper crucible to create a molten alloy, e.g., using induction or arcmelting. The GBE system under vacuum cools the copper crucible, e.g.,using water cooling, to create an ingot from the molten alloy whichsolidifies, continuously, from the bottom upwards. The GBE system maymelt the elements to create the molten alloy and cool the molten alloyto create the ingot. The GBE system may melt the elements under 1.8 barof absolute pressure, e.g., in an argon atmosphere. The GBE system maycool the molten allow in a vacuum that is greater than 10-1 bar.

In some examples, the GBE system re-melts the ingot in the coppercrucible by heating the ingot using arc melting to product a re-meltedmolten alloy. The GBE system cools the re-melted molten alloy to createa re-melted ingot which solidifies, continuously, from the bottomupwards.

The arc melting or re-melting process may create a high performancealloy, a high purity alloy, or both, for manufacturing a rare earthsintered magnet with specific properties, e.g., a high Br of 1.3 T ormore, a high coercivity of 2000 kA/m or more, or both, with a modifygrain boundary phase. A GBE system may use a melting or a re-meltingprocess to reduce gas content, e.g., contamination, reducemacro-segregation and microsegregation, increase yield, increaseproperty reproducibility, or two or more of these. For instance, the GBEsystem may increase property reproducibility because of a limited moltenmetal alloy pool produced during re-melting which allows GBE systemcontrol of ingot solidification rates, e.g., the segregation and thechemical composition of the molten metal alloy.

In some examples, the GBE system may form theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % precursor usingthe RF melted ingots and cool the melted ingots naturally, e.g., at roomtemperature, without a cooling source, or both, in an alumina crucible.The GBE system may melt the ingots multiple times, e.g., twice, toensure homogenous elemental distribution of the elements in the meltedingots. The GBE system may verify the distribution of the elements inthe final precursor using inductive coupled plasma (ICP). The density ofthe Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % precursor maybe 8.21 g/cm³. The GBE system may verify the density of the precursorusing Archimedes principle.

In some implementations, the GBE system may use a spray atomizingapparatus with a high velocity gas jet on a free fallingNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % melt stream toform the precursor from the rare earth transitional elemental additivematerial. For instance, the high velocity gas jet may be an inert gas,e.g., Ar, Ne, He, N, or a combination of two or more of these, have avelocity of 500 m/s, or both. The high velocity gas jet may fragment thefree falling Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % meltstream into small droplets, each with a loss of about 2 wt. % of rareearth materials and an oxygen concentration of up to 0.04 wt. %.

The high velocity gas jet forms, propels and cools the droplets and maycreate droplets with nearly spherical submicron and micron particlesize. This may create Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03)at. % particles with a large surface area to volume ratio, e.g., whichthe GBE system may use to produce the composite powder using theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % precursor and theNd₂Fe₁₄B powder or Nd₂(FeCo)₁₄B powder. The process of suitable powdersize preparation of the Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03)at. % is not limited only to spray atomizing but can be achieved also byspray pressure atomization, two-fluid atomization, rotary atomization,effervescent atomization, electrostatic atomization, ultrasonic andwhistle atomization.

FIG. 10 shows an example of a spray atomizing apparatus 1000 that mayallow the melted Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. %precursor 1002 to fall through a bottom aperture 1004 of the sprayatomizing apparatus. For instance, the melted precursor 1002 may fallthrough the aperture 1004 due to gravity, in a high velocity gas jet,e.g., 0.18-0.58 MPa, on a free fallingNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % melt stream. Thehigh velocity inert gas jet 1006 rapidly fragments a volume of themelted Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % precursor1002 into large number of small droplets. The small droplets may have anoxygen concentration of up to 0.04 wt. %, about 2 wt. % loss of rareearth material, and a powder size of 140-280 micrometers. The density ofthe measured Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. %powder of the precursor may be 8.08 g/cm3. In some examples, a densityof the droplets varied from 95-98% of the theoretical value, e.g., 8.375g/cm3 for a single phaseNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % droplet.

The GBE system may then place the atomized powder or melted dropletsinto a hydrogen mixing reactor together with an Nd₂Fe₁₄B sinter block toproduce the composite mixture. The hydrogen mixing reactor may beevacuated and then introduce hydrogen gas into the processing chamberwith the precursor and the Nd₂FeB sinter block for 12 hours. Thehydrogen is absorbed by the Nd—Fe—B sinter block magnet body, by theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % precursor, e.g.,powder or droplets, or both, causing expansion of the correspondingmaterial and the corresponding material to break apart into a powder,e.g., a coarse powder. The hydrogen mixing reactor processing may causethe Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % precursor torelease entrapped gas accumulated during the atomization process. Insome examples, hydrogen mixing reactor may process the precursor and theNd₂Fe₁₄B sinter block under absolute pressure of about 2 bar with aconstant feed of hydrogen into the processing chamber until the processis complete, e.g., when there is no change of pressure detected. The GBEsystem may then heat the powders in-situ to 580° C. to partially desorbthe composite Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at.%/Nd—Fe—B mixture, e.g., to cause the release of hydrogen from the bodyof the powder particles. The GBE system may then transfer the compositepowder into an argon atmosphere transfer-box, e.g., to move thecomposite powder to another component of the GBE system.

In some implementations, the GBE system may further process thecomposite powder, e.g., the Nd11.92Dy42.32Co38.39Cu5.34Fe2.03 at. %precursor and Nd—Fe—B or Nd—Fe—Co—B, using high energy milling, ballmilling or jet milling. The GBE system may process the composite powderuntil the powder is a homogeneous mixture and has a powder size of 2-4.5μm.

The rare earth transitional elemental additive material may include oneor more elements from Nd, Pr, Dy, Co, Cu, and Fe. Some examples ofranges for the combinations of the elemental additive material includeNd: [6.1717, 11.8917] (at. %); Pr: [1.5495, 4.821] (at. %); Dy: [0.2132,5.3753] (at. %); Co: [0, 4.0948] (at. %); Cu: [0.0545, 0.2445] (at. %);and Fe: [81.1749, 85.867] (at. %). In some implementations, a range forthe amount of rare earth elements in the rare earth transitionalelemental additive material may be [13.236, 16.407] (at. %) or [28.82,33.7] (wt. %). In some examples, small amounts of 0, C, or both, may beadded to the rare earth transitional elemental additive material duringprocessing of the rare earth transitional elemental additive material.The ranges of the rare earth transitional elemental additive material inwt. % may be: Nd: [12.726, 24.85] (wt. %); Pr: [3.1638, 9.677] (wt. %);Dy: [0.506, 12.49] (wt. %); Co: [0, 3.4963] (wt. %); Cu: [0.0506,0.2248] (wt. %); and Fe: [63.6551, 70.009] (wt. %).

In some examples, the GBE system replaces the old Nd-rich grain boundaryphase with the rare earth transitional elemental additive material byany appropriate method. For instance, when the Nd-rich grain boundaryphase is oxidized and does not react with H₂ during hydrogen processing,the GBE system may sieve the Nd₂Fe₁₄B powders to remove the Nd-richgrain boundary phase. In some examples, the GBE system may sieve theNd₂Fe₁₄B powders to remove ultra-fine particles, e.g., that have ananometer size less than one micrometer, that include the Nd-rich grainboundary phase particles. In some implementations, the GBE system mayfragment the Nd₂Fe₁₄B sintered magnet separately from the rare earthtransitional elemental additive material so that some of the additivematerial is not removed during the sieving process.

The rare earth transitional elemental additive material may be chosenusing an elemental analysis of the magnetic material composition and adatabase of formulas determined by experiment and extrapolation to besuitable for achieving a predefined target formulation and magneticperformance or any other appropriate method. For instance, the databasemay include historical data indicating composition properties ofmagnetic material and rare earth transitional elemental additivematerial added to the magnetic material to achieve desired propertiesfor a resulting sintered magnet product.

In some examples, a system may use the following formulas to determinethe total amount of elements in the sintered magnet product, e.g.,created in step 918. For instance, a final value f1 of Nd in thesintered magnet product may be f1=w*p1+(1−w)*a1 when w=[81, 99.9] (at.%), 1−w=[0.1, 19] (at. %), p1 is the amount of Nd in the initial alloy,and a1 is the amount of Nd in the elemental additive material. A finalvalue f2 of Pr in the sintered magnet product may be f2=(1−w)*a2 when a2is the amount of Pr in the elemental additive material. A final value f3of Dy in the sintered magnet product may be f3=(1−w)*a3 when a3 is theamount of Dy in the elemental additive material. A final value f4 of Coin the sintered magnet product may be f4=(1−w)*a4 when a4 is the amountof Co in the elemental additive material. A final value f5 of Cu in thesintered magnet product may be f5=(1−w)*a5 when a5 is the amount of Cuin the elemental additive material. A final value f6 of Fe in thesintered magnet product may be 6=w*p2+(1−w)*a6 when p2 is the amount ofFe in the initial alloy and a6 is the amount of Fe in the elementaladditive material. A final value f7 of O in the sintered magnet productmay be f7=w*p4+(1−w)*a7+E_O when p4 is the amount of O in the initialalloy, e.g., after processing of the alloy, a7 is the amount of O in theelemental additive material, and E_O is the amount of oxygen addedduring processing of the combined alloy and elemental additive materialto create the sintered magnet product. A final value f8 of C in thesintered magnet product may be f8=w*p5+(1−w)*a8+E_C when p5 is theamount of C in the initial alloy, e.g., after processing of the alloy,a8 is the amount of C in the elemental additive material, and E_C is theamount of carbon added during processing of the combined alloy andelemental additive material to create the sintered magnet product. Afinal value f9 of B in the sintered magnet product may be f9=w*p3 whenp3 is the amount of B in the initial alloy.

In some examples, the final value f1 of N may be in the range [7.3635,11.1038] (at. %). The final value f2 of Pr may be in the range [1.445,3.6323] (at. %). The final value f3 of Dy may be in the range [0.199,4.0535] (at. %). In some implementations, a total amount of the rareearth elements in the rare earth transitional elemental additivematerial may be in the range [12.66, 15.03] (at. %). The final value f4of Co may be in the range [0, 3.098] (at. %). The final value f5 of Cumay be in the range [0.0508, 0.1849] (at. %). The final value f6 of Femay be in the range [76.3928, 80.0287] (at. %). The final value f7 of 0may be in the range [0.09, 4.0] (at. %). The final value f8 of C may bein the range [0.001, 1.0] (at. %). The final value f9 of B may be in therange [5.7493, 6.4244] (at. %).

In some examples, the final value f1 of N may be in the range [16.125,24.575] (wt. %). The final value f2 of Pr may be in the range [3.125,7.75] (wt. %). The final value f3 of Dy may be in the range [0.5, 10](wt. %). In some implementations, a total amount of the rare earthelements in the rare earth transitional elemental additive material maybe in the range [29, 33] (wt. %). The final value f4 of Co may be in therange [0, 2.8] (wt. %). The final value f5 of Cu may be in the range[0.05, 2.8] (wt. %). The final value f6 of Fe may be in the range[64.6705, 69.2205] (wt. %). The final value f7 of O may be in the range[0.01, 0.9] (wt. %). The final value f8 of C may be in the range [0.01,0.5] (wt. %). The final value f9 of B may be in the range [0.95, 1.05](wt. %).

At 912, the process fragments and homogeneously mixes the powder bysuitable means. In some implementations, this is accomplished by jetmilling to a target particle size between about 1 to about 4 microns.The powder may be fragmented, homogenized, or both using any appropriatefragmentation apparatus, such as those described in more detail above.In some implementations, steps 910 and 912 may be performedconcurrently. In some implementations, instead of adding the rare earthtransitional elemental additive material minor fraction to the batch tobe hydrogenated, the rare earth material is separately hydrogenated andmixed in at 912. In some examples, the rare earth transitional elementaladditives may be milled separately and added after milling of themagnetic material, e.g., after 912, during which the magnetic materialis preferably divided sufficiently to form a powder in the range ofbetween about 1 to about 50 microns using high pressure e.g., 60 bar.

In some implementations, the GBE system may use a jet milling system,e.g., after using a hydrogen mixing reactor, to homogenize and form thecomposite power with a results powder size of 2 to 4.5 μm.

In some implementations, a GBE system homogenizes theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % powders with theNd₂Fe₁₄B powders to obtain uniform distribution of a new grain boundaryelemental concentration within a bulk Nd—Fe—B-type body, e.g., a finalsintered magnet. In some examples, the GBE system may use homogenizationand uniform distribution to make final sintered magnets from differentinitial sintered magnets more uniform.

In some examples, homogenization may reduce grain size, may enclose,e.g., surround, the original Nd—Fe—B powders, e.g., grains, withNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % powders, or both.In some implementations, homogenization may include a comminuting stepin which the GBE system grinds a coarse powder ofNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % and a coarsepowder of the initial Nd—Fe—B sintered magnet into a fine powderconsisting of small particles, e.g., with a size between about 0.5 μm toabout 5 μm by applying a mechanical force, e.g., H2, to the materials.The application of the mechanical force to the materials, e.g., theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % and the Nd—Fe—Bsintered magnet, may create particles from the materials and cause anincrease in the surface area of the particles. In some examples, thehomogenization may cause a random distribution of theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % particles withinthe Nd2Fe14B particles. In some examples, a GBE system may homogenizethe distribution of the Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03)at. % powders within the Nd₂Fe₁₄B powder using mechanical mixingdevices, including a spiral mixer, V-blender or a twin-shell V-blender,jet milling, ball milling, high-energy milling or mechano-chemicaldevices such as hydrogen mixing reactor.

At 914, the process sieves larger particles, e.g., about 1 mm, out ofthe fragmented material. For instance, the GBE system processes a powderoxidized fraction by sieving out larger particles, such as particlesbetween about 500 microns to about 2 mm, from the fine powder. Thisprocedure is effective for removing the oxidized fraction because of thehardness of oxides relative to the major fraction of recovered rareearth magnet material which prevents the oxidized particles fromfragmenting into smaller parts. For example, hydrogenation, milling, jetmilling, crushing, or another appropriate method, may be less apt tobreak up oxides leaving their size distribution larger and makingpossible to eliminate or reduce their proportion in the fine powder bysieving.

At 916, the process presses and aligns the fine powder to form a greencompact by filling a press and establishing a magnetic field in thepress, and at 918 the process sinters and heat treats the green compactto form a final sintered magnet product. For instance, the GBE systemcreates a green compact with the rare earth transitional elementaladditive materials in the grain boundary between the 2:14:1 phase grainsinitially created in the cast alloy flakes. The rare earth transitionalelemental additive materials are distributed homogeneously between the2:14:1 phase grains. The final sintered magnet product may be acomposite of high density, e.g., from 7.5 to 7.6 g/cm³.

The rare earth transitional elemental additive materials may form a newgrain boundary phase, e.g., that is substantiallyNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. %. In someimplementations, the new grain boundary phase substantially replaces theinitial grain boundary phase that was previously included in the initialsintered magnet. For instance, theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % grain boundaryphase substantially replaces the old Nd-rich grain boundary phase. Thenew grain boundary phase may have increased grain boundary cohesion withincreasing volume fraction and act as a nucleation site for theformation and growth of reversed nucleation sides within the finalsintered magnet product. In some examples, the new grain boundary phasemay inhibit the probability of surface defects on the individual grainsof the final sintered magnet.

In some implementations, the GBE process may use powder blending and ahydrogen mixing reactor to prepare composite mixture of Nd₂Fe₁₄B alloyand Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % prior toremoving the Nd-rich phase from the alloy. The GBE process may create afinal sintered magnet with a new grain boundary phase that exhibitsdensity improvements as the volume fraction of the new grain boundaryphase increases from 10 to 90 vol. %, e.g., usingNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % as the rare earthtransitional elemental additive material. In some examples, the rareearth transitional elemental additive material may act as a sinteringaid, e.g., in the range of 10 to 30 vol. % and 50 to 90 vol. % of thegrain boundary phase, by making the sintering process more efficient,providing better mechanical properties for the final sintered magnet, orboth. In some examples, when a GBE system uses the GBE process to add anew grain boundary phase to a final sintered magnet, the final sinteredmagnet has improved corrosion resistance.

For instance, FIG. 11 shows a graph comparing the corrosion resistanceof a GBE final magnet with other Nd—Fe—B magnets, e.g., waste sinteredNd—Fe—B magnets. For instance, FIG. 11 shows the weight loss inmilligrams per cm2 of surface area of the following sintered magnets,(a) a final GBE Nd—Dy—Fe—Co0.78-B magnet with 1 at. % of Nd/Pradditions, (b) a Nd—Dy—Fe—Co0.9-B magnet, (c) a Nd—Dy—Fe—Co0.7-B magnet,(d) a Nd—Dy—Fe—Co0.5-B magnet, and (f) an Nd—Fe—B traditional magnet.The magnets were tested using a highly accelerated stress test at 130°C. and 2.7 bar in water vapor similar to IEC 68-2-66, with an exposuretime of twenty days, in dependence on the Co-concentration of themagnets.

A GBE system added fresh additive material to waste Nd—Fe—B powder tocreate the GBE final magnet with restored magnetic performance,microstructure, and density. The fresh additive material may be, e.g.,Nd and Pr or Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % orNd with two additional material, or Pr with two additional materials.The additional materials may be selected from Fe, Co, Cu, Dy, Nd, or Pr.The GBE final magnet has improved corrosion resistance compared to theother magnets tested. In this example, the corrosion resistance beginsto increase with inclusion of 10 vol. % of newly modifiedNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % grain boundaryphase to replace the old Nd-rich grain boundary phase.

In some implementations, the starting composition of the initialsintered magnet, e.g., a waste Nd—Fe—B sintered material or a newsintered magnet, may include Pr at 5.585 wt. %, Nd at 23.615 wt. %, Dyat 0.4 wt. %, Co at 0.79 wt. %, Cu at 0.1 wt. %, B at 0.98 wt. %, C at0.0704 wt. %, O at 0.059 wt. %, and Fe at 68.4006 wt. %. The endcomposition of the final sintered magnet may include Pr at 5.22 wt. %,Nd at 22.88 wt. %, Dy at 0.93 wt. %, Co at 1 wt. %, Cu at 0.12 wt. %, Bat 1 wt. %, C at 0.13 wt. %, O at 0.12 wt. %, and Fe at 68.6 wt. %.

In some implementations, a GBE system may design an appropriate grainboundary engineering approach. For instance, a GBE system may use globaltrend information about a degree of equilibrium of non-ordered orordered grain boundaries to reduce an overall grain size by grainboundary segregation engineering, leading to a reduction in grainboundary energy and grain boundary mobility. In some examples, the GBEsystem may require crystallographic and elemental analysis ofsegregation or quantification of overall additions of volume fraction ofnew grain boundary Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at.% between grain interiors and the abutting Nd₂Fe₁₄B grain boundary, orboth, as starting information for a possible grain boundary segregationand microstructure information for a grain growth inhibition. In someimplementations, Grain Boundary Engineering results in a homogeneouslydistribution of the Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at.% precursor powder through the final magnet body, e.g., throughout thegrain boundary.

In some implementations, the GBE system may use the process 900, some ofthe steps of the process 900, or another appropriate method to modifythe grain boundary of another type of magnet. For instance, the GBEsystem may modify the grain boundary of an Nd₂(FeCo)₁₄B sintered magnetor an Sm₂Co₁₇ sintered magnet. In some examples, when modifying thegrain boundary of an Sm₂Co₁₇ sintered magnet, the GBE system may add acombination of one or more of Sm, Co, Zr, Fe, or Cu.

Example 2

Magnets created with the GBE technique have improved temperatureperformance. For example, magnets created with the GBE technique haveimproved thermal stability and improved magnetic properties. Recycledmagnets, such as Nd—Fe—B recyclates e.g., from end-of-life products, mayhave improved thermal stability compared to the input material, e.g.,virgin magnets, processed to create the recycled Nd—Fe—B magnets.Magnets made from input virgin, or mostly virgin, Nd—Fe—B magneticmaterial and processed with the GBE technique may have improved thermalstability compared to magnets made with other processes.

Table 5 shows the ICP composition of two starting magnets, startingmagnet 1 and starting magnet 2, and of two final magnets made from thestarting magnets, final magnet 1 and final magnet 3. Final magnet 1includes 0.5 at. % addition of additive material, added using the GBEtechnique, and final magnets 2 and 3 include 2 at. % and 3 at. %,respectively, addition of additive material, added using the GBEtechnique.

The starting magnet 1 was used as the starting magnetic material for thefinal magnet 2, with 2 at. % additions, and the final magnet 3, with 3at. % additions. The starting magnet 2 was used as the starting magneticmaterial for the final magnet 1. The starting magnets 1 and 2 were madefrom virgin magnetic material, i.e., and were not recycled magnets.

TABLE 5 ICP of magnets (wt. %) ± 0.08 wt. % Starting Starting FinalFinal Magnet 1 Magnet 2 Magnet 1 Magnet 3 Pr 5.75 7.14 5.64 6.43 Nd23.91 21.07 22.5 21.63 Dy 0.31 0.4 0.95 3.42 Fe 67.85 69.10 68.2 64.75Ga 0.11 0.11 0.1 0.1 Zr 0.1 0.12 0.09 0.11 Al 0 0.25 0.1 0.28 Co 0.730.55 1 1.74 Cu 0.12 0.16 0.13 0.32 B 0.98 0.96 1.05 0.97 C 0.074 0.0690.12 0.12 O 0.069 0.067 0.12 0.13 Density 7.55 7.55 7.55 7.55 (g/cm³)

Testing was performed to determine the thermal stability of the startingmagnets and the final magnets, i.e., from 20 to 200° C., using apermeameter. Each of the magnets had a cylindrical shape and a length todiameter ratio L/D of 0.9 cm/1 cm=0.9, e.g., the length to diameterratio L/D for each of the magnets is the same. Testing proceed byplacing each of the magnets into the permeameter and measuring therespective magnet's remanence and coercivity at room temperature.Testing continued by increasing the temperature and holding thetemperature at each stage for fifteen minutes before again measuring therespective magnet's remanence and coercivity.

The starting magnet 1 and the starting magnet 2 had a demagnetizationcurve knee, e.g., the point at which remanence drops abruptly to zero,barely above 80° C. The final magnet 1 had a demagnetization curve kneeat 120° C. The final magnet 3 had a demagnetization curve knee above200° C. These results indicate that both the final magnet 1 and thefinal magnet 3 are more thermally stable than both of the startingmaterials 1 and 2 and that the final magnet 3 is the most thermallystable of the four magnets tested.

The reversible loss coefficients α and β plotted against temperaturerepresent the reversible loss of remanence and coercivity when a magnetis operating at a particular temperature. For example, Table 6 belowsummaries the temperature range and reversible loss α and the coercivityreversible loss β for starting magnet 1 and final magnet 3.

TABLE 6 Reversible loss for starting magnet 1 and final magnet 3Remanence reversible loss α α at 80° C. α at 120° C. α at 140° C. α at160° C. α at 180° C. α at 200° C. Starting −0.12 −0.12 −0.13 −0.141−0.14 −0.14 Magnet 1 Final −0.019 −0.062 −0.06 −0.09 −0.09 −0.11 Magnet3 Coercivity reversible loss β β at 80° C. β at 120° C. β at 140° C. βat 160° C. β at 180° C. β at 200° C. Starting −0.82 −0.68 −0.62 −0.57−0.53 −0.50 Magnet 1 Final −0.60 −0.56 −0.53 −0.51 −0.49 −0.47 Magnet 3

The temperature at which magnetic flux φ for a magnet decreases by nomore than 5% while held at that temperature and remains reversibleduring cooling is defined at T5%. To determine this temperature for themagnets, a flux reading for the magnets was taken after the magnets wereheld at various temperatures in a range from 20 to 200° C. for twohours. When testing the final magnet 2 and the final magnet 3, bothmagnets had a maximum temperature T5% at which the magnetic fluxdecreased by no more than 5% of 200° C.

FIGS. 12A-B show remanence reversible losses α for starting and finalmagnets. For instance, FIG. 12A shows remanence reversible losses α forstarting magnet 1, final magnet 2, and final magnet 3. For example, thefinal magnet 3 has better α at each temperature range with theimprovement ranging from 84% at 80° C. to 25% at 200° C. compared to thestarting magnet 1. The final magnet 2 had improved α at each temperaturerange compared to the starting magnet 1. FIG. 12B shows remanencereversible losses α for starting magnet 2 and final magnet 1. The finalmagnet 1 has a better α at each temperature range compared to thestarting magnet 2.

FIGS. 13A-B show coercivity reversible losses β for starting and finalmagnets. The final magnet 1 has decreasing β as temperature increases.For example, as temperature increases the coercivity loss saturates.

For instance, FIG. 13A shows coercivity reversible losses β for startingmagnet 1, final magnet 2, and final magnet 3. FIG. 13B shows coercivityreversible losses β for starting magnet 2 and final magnet 1. Therecycled final magnets 2 and 3 showed improved value for β at eachtemperature when compared with the starting magnets. For example, thefinal magnet 3 has better β at each temperature range with theimprovement ranging from 26% at 80° C. to 6% at 200° C. compared to thestarting magnet 1.

The final magnet 1, the final magnet 2, and the final magnet 3 have anoverall improvement in coercivity (iHc) value. For example, the averagecoercive force (iHc) improvements for the final magnets 1, 2, and 3,respectively, across the whole temperature range, are 16%, 70% and 128%when compared to the respective starting magnets.

Table 7 shows the reversible coefficients α and β for Nd—Fe—B magnetsmade from virgin material and recycled Nd—Fe—B magnets. The recycledmagnets have improved α and β compared to the magnets made from virginmaterial. Specifically, the recycled magnets have a remanence reversibleloss α at 80° C. that is a factor of ten better than the magnets madefrom virgin material. At 140° C. the recycled magnets have a remanencereversible loss α that is twice as good as the romance reversible loss αof the magnets made from virgin material.

TABLE 7 Comparison of α and β in magnets made from virgin material andrecycled magnets Br %/° C., α80 to α200 iHc %/° C., β80 to β200 StartingMagnets −0.10 to −0.13 −0.55 to −0.65 Recycled Magnet −0.02 to −0.11−0.47 to −0.60

In some implementations, the more elemental addition added to magneticmaterial using the GBE process, the more thermally stable the resultingfinal product, compared to starting magnetic material. In some examples,the GBE process may result in improved temperature stability andcoercivity compared to starting material or magnetic material createdwith a different process.

Example 3

In some examples, waste magnets may be processed using the GBEtechnique. For instance, a GBE system may create magnets, e.g., usingsteps 902 through 908, which includes the creation of waste magnets. Insome examples, the waste magnets may be created using another process ormay be received by a GBE system from another system.

The GBE system processes the waste magnets using steps 910 through 918described above. In some implementations, the waste magnets and therecycled magnets may have properties similar to those shown in Table 8below. As described above, the quantity and types of elements includedin the additive material may be adjusted for each of the different wastemagnets to result in a final magnet with the same properties. In someexamples, 1 at. % of Nd/Pr was added to the particles formed from eachof the waste magnets.

TABLE 8 ICP of magnets (at. %) Waste Waste Waste Waste Magnet 1 Magnet 2Magnet 3 Magnet 4 Final Magnet Nd 10.95 10.94 10.55 8.34 10.95 Pr 3.083.08 2.7 2.14 2.8 Dy 0 0.41 0.2 3.62 1.07 Tb 0 0 0 0 0.01 Fe 78.11 74.6577.91 76.24 75.79 B 5.77 5.64 5.97 6.05 5.91 Co 0.52 3.36 1.05 1 1.5 Al0.72 0.36 0.29 1.45 0.71 Cu 0.01 0.14 0.1 0.1 0.09 Ga 0 0.21 0.09 0.090.1 O 0.41 0.83 0.6 0.43 0.58 C 0.43 0.38 0.54 0.54 0.49

The remanence (Br) of the final magnet may be 1.25 T. The coercivity(iHc) of the final magnet may be 1710 kA/m. The energy product (BHmax)of the final magnet may be 303 kJ/m³. The final magnet product may havea density of 7.55 g/cm³.

FIG. 14 shows a graph of example properties of the final magnetdescribed in example 2, e.g., made from mixed grade waste magnets with 1at. % Nd/Pr mixture additions. For instance, the final magnet mayinclude an Nd/Pr grain boundary phase that replaced an old Nd-rich grainboundary phase.

FIG. 15 shows some examples of magnetic properties of waste sinteredmagnets and recycled magnets, e.g., processed using the GBE process. Forinstance, multiple waste sintered magnets were collected from consumerproducts in which the waste sintered magnets had different elementalcompositions, e.g., see Table 8 for an ICP analysis of the wastesintered magnets.

In this example, the coercivity is controlled by the nucleation ofso-called reverse domains at the surface defects of the individualgrains in the magnets, e.g., both the waste sintered magnets and therecycled magnets. A GBE system may inhibit the formation of thesedefects by adding a new grain-boundary phase, e.g., using Nd/Pr additivematerial, which, after processing, surrounds the Nd—Fe—B phase grains,and may minimize the occurrence of surface defects, such as cracks,bumps, pits, etc.

In some implementations, the GBE system may create the recycled magnetsto have the same or higher coercivity, as shown in FIG. 15, than thewaste sintered magnets. In some examples, the coercivity of a startingmagnet before GBE is about 1400 kA/m and the coercivity of a magnetprocessed using GBE is 1700 kA/m. For instance, the following GBEprocesses may recover or improve the coercivity of the waste magnetswhen forming the recycled magnets: a) the preparation of the compositepowder from Nd/Pr additive material and the Nd—Fe—B waste magnet, b)adjustment of processing parameters, e.g., jet milling, sinteringparameters, and annealing, or c) both. The GBE system may improve theperformance of the recycled magnets, compared to the waste sinteredmagnets, by hindering of the formation of reverse-domain nucleationsites when the new Nd/Pr grain-boundary zones form a more uniformencapsulation of the Nd2Fe14B matrix-phase grains. In some examples, theGBE system may “clean” the “old” Nd-rich phase grain boundary, which mayhave acted as a nucleation site for the formation and growth of reversedomains within the Nd—Fe—B-type sintered magnets, with the new Nd/Prgrain boundary phase because of the increased grain boundary cohesionwith an increasing volume fraction of the new Nd/Pr grain-boundaryphase.

Example 4

In some implementations when a GBE system uses a spray atomizingapparatus, the GBE system may initially use a single phaseNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % powder with ameasured density of 8.375 g/cm³, and a variance from the theoreticalvalue of about 95 to 98%. The spray atomizing apparatus may create anNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % precursor with adensity of 8.08 g/cm³. The GBE system may then transfer theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % precursor, e.g.,the atomized powder, to a hydrogen mixing reactor with an Nd2Fe₁₄Bsintered block to produce a composite powder from the precursor and thesintered block.

For instance, after the Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03)at. % precursor and the sintered block are placed in the hydrogen mixingreactor, the hydrogen mixing reactor is evacuated and then hydrogen maybe introduced for twelve hours. The hydrogen is absorbed by the Nd₂Fe₁₄Bsintered block and the Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03)at. % precursor powder causing the sintered block to expand and breakapart into a coarse powder and theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % precursor powderto further break apart and release entrapped gas accumulated during theatomization process. The hydrogen mixing process may occur under anabsolute pressure of about 2 bars with a constant feed of hydrogen intothe hydrogen mixing chamber until the mixing process is complete. TheGBE system may then heat the powders in the hydrogen mixing chamber,e.g., in-situ, to 550° C. to partially desorb the composite mixture,e.g., to cause the release of hydrogen from the body of the powderparticles.

Example 5

In some implementations, final magnet products produced using the GBEprocess may have improved temperature stability compared to othermagnets, e.g., other recycled magnets. For instance, a GBE system maycreate a powder from Nd—Fe—B material, e.g., using a hydrogen mixingprocess, and mix the powder withNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % to replace theold Nd-rich grain boundary phase with a newNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % grain boundaryphase. The mixing of the powder with theNd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % may homogenizethe new Nd_(11.92)Dy_(42.32)Co_(38.39)Cu_(5.34)Fe_(2.03) at. % grainboundary phase throughout the Nd—Fe—B powder while the old Nd-rich grainboundary phase is removed, e.g., by sieving, air blowing, vibration,shape separation, density gradient separation, twin cylindrical gravityseparation, or a combination of two or more of these.

The GBE system may obtain a composite raw material powder and orient thecomposite raw material powder in a magnetic field, e.g., interatmosphere under magnetic field orientation. While the composite rawmaterial powder is oriented in the magnetic field, the GBE system maycompression-mold the powder and charge the magnetic field to obtain amolded composite body. The GBE system may sinter the molded compositebody to obtain a final sintered magnet product.

FIG. 16 shows examples of demagnetization curves of a magnet that hasnot been processed using the GBE process. FIG. 17 shows examples ofdemagnetization curves of a magnet that has been processed using the GBEprocess, e.g., and has an improved temperature stability as indicated bythe better squareness factor in FIG. 17 compared to FIG. 16. Forinstance, at 25° C., the coercivity of the starting material, as shownin FIG. 16, is between 1000 and 1100 kA/m and the coercivity of a finalmagnet, as shown in FIG. 17, is between 1800 and 1900 kA/m. The changein the content from the magnet whose properties are shown in FIG. 16compared to the magnet whose properties are shown in FIG. 17, e.g., from0.4 wt. % Dy to 3.4 wt. % Dy, is due to the rare earth elementaladditive material. In some examples, the content of Cu, Nd, Co, or twoor more of these, may be higher in a magnet processed using the GBEprocess compared to a starting magnet or starting magnetic material.

Example 6

In some implementations, when a system performs grain boundaryengineering on scrap material, the scrap material may contain a highamount of Dy in the grain boundary, the Nd2Fe14B1 matrix phase, or both.The high amount of Dy may contribute to lower magnetic performance of afinal magnetic product made from the scrap material. To increase theremanence (Br) in a final magnetic product made from the scrap material,the system may remove Dy from the scrap material by replacing the Dywith Fe, e.g., the system may push Dy out of the scrap material bypumping Fe into the scrap material. The system may use Fe in an additivematerial mixed with the scrap material to remove Dy from the scrapmaterial, e.g., during a mixing process.

The system may mix an additive material that does not include any Dywith the scrap material. The additive material may include a high amountof Fe, Nd, Co, or two or more of these, as shown in Table 9 below. Forinstance, the system may add Fe, remove Dy, or both, to and from thescrap material to get as close to Nd2Fe14B1 phase as possible to ensurea high magnetic performance of a final magnetic product. For example,the system may add Fe, remove Dy, or both, to and from the scrapmaterial to increase remanence (Br) and decrease coercivity (iHc).

Table 9 shows quantities, in weight percent, of two starting scrapmaterials, s1 and s2, additive material, a, and a final magneticproduct, f, made from the two starting scrap materials and the additivematerial. For instance, s1(e) indicates the quantity, in weight percent,of element e in the first starting scrap material s1 and s2(e) indicatesthe quantity, in weight percent, of element e in in the second startingscrap material s2 in Table 9 below. The quantity in weight percent ofelement e in the additive material a is indicated by a(e) and thequantity in weight percent of element e in the final magnetic product fis indicated by f(e) in Table 9 below.

Some minor elements are omitted from Table 9 for clarity. The quantitiesin Table 9 have +/−0.01 to 0.08 wt. % error (due to ICP readings).

TABLE 9 wt. % of magnetic material Nd Pr Dy B Co Al Cu Ga O C Fe Alls₁(e) 18.08 4.52 6.50 1.02 2.94 0.12 0.18 0.21 0.20 0.10 66.13 100 s₂(e)17.55 5.85 4.20 0.96 0.19 0.40 0.15 0.10 0.07 70.53 100 a(e) 15.20 1.5083.30 100 f(e) 17.29 4.15 4.28 1.00 1.55 0.21 0.13 0.08 0.18 0.10 71.02100

In the example shown in Table 9, a system mixes the final magneticproduct from 40 wt. %*s1+40 wt. %*s2+20 wt. %*a, e.g., such that, foreach element e in the final magnetic product f, f(e)=40 wt. %*s1 (e) 40wt. %*s2(e) 20 wt. %*a(e). For instance, the system mixed 40 kg s1, 40kg s2, and 20 kg a to create 100 kg of the final magnetic product f.

Table 10 indicates the magnetic properties of the two startingmaterials, s1 and s2, as well as the final magnetic product, f. Forinstance, Table 10 shows that a system that mixes 40 wt. %*s1 with 40wt. %*s2 and 20 wt. %*a to create the final magnetic product f, mayimprove the performance of the final magnetic product f compared to oneor both of the two starting materials. For instance, the system mayincrease the remanence (Br), increase the energy product (BHmax),decrease the average coercivity (iHc), or two or more of these.

TABLE 10 magnetic properties Br (T) iHc (kA) BH(max) s₁ 1.25 2345 300 s₂1.30 1820 330 f 1.35 (calculated) 2013 (calculated) 360

In some implementations, a GBE method provides for the addition of 0.1to 19 wt. % of one or more rare earth elemental additives to acomposition or method described herein. In another aspect, a methodprovides for the addition of about 0.1 wt. %, about 0.2 wt. %, about 0.3wt. %, about 0.4 wt. %, about 0.5 wt. %, about 1 wt. %, about 2 wt. %,about 3 wt. %, about 4 wt. %, about 5 wt. %, about 6 wt. %, about 7 wt.%, about 8 wt. %, about 9 wt. %, about 10 wt. %, about 11 wt. %, about12 wt. %, about 13 wt. %, about 14 wt. %, about 15 wt. %, about 16 wt.%, about 17 wt. %, about 18 wt. %, or about 19 wt. % of one or moreelemental additions or a combination of one or more elemental additionsto a composition or method described herein. In yet another aspect, amethod provides for the addition of about 0.1-0.5 wt. %, about 0.1-1 wt.%, about 0.5-1 wt. %, about 1-2 wt. %, about 1-3 wt. %, about 1-5 wt. %,about 1-8 wt. %, about 1-12 wt. %, bout 1-15 wt. %, about 1-19 wt. %about 2-4 wt. %, about 2-6 wt. %, about 2-12 wt. %, about 2-19 wt. %,about 3-5 wt. %, about 3-8 wt. %, about 3-15 wt. %, and about 3-19 wt. %of one or more elemental additions or a combination of one or moreelemental additions to a composition or method described herein.

In some implementations, the hydrogen mixing process of the initialsintered magnet blocks, and optionally the additive material, may beperformed at 20-150° C. at 1 to 60 bar pressure under a hydrogenatmosphere. The initial sintered magnet blocks may be created using anyappropriate process or may be purchased from a vendor, to name a fewexamples. After that, the powder created from the hydrogen mixingprocess may be heated, preferably in situ, to 550-600° C. to partiallydegas the mixture. The average particle size in the powder generated bythe mixing step may be in the range of 1 μm to 2000 mm. If a pressure of50 bar is used, the average particle size may correspond to a grainsize, e.g., 2-8 present in the original magnetic material, and particlesin the range of 500 μm to 2000 mm that have not reacted with hydrogendue to oxidation. The powder may be sieved to remove the oxidized coarserare earth powders.

In some implementations, the hydrogen mixing process employs a highenough pressure to ensure that particles are small enough for a finalmagnet and the jet milling operation can be skipped. In this example,the sieving to remove larger particles, thereby to remove particles withhigher concentration of oxygen, may be advantageous. The sieving may beeffective because the oxides constitute a harder fraction of therecovered material from the magnet and resist reduction to smallerparticle sizes.

Further mixing and homogenization of the magnetic powder mixture may betransferred to a roller mill for further homogenization of the mixture.The milled material may be lubricated, for example, with 1% of Znstearate, during roller milling. After the roller milling step, magneticpowders may be sieved to further remove any remaining rare earth oxide.In some implementations, the sieving may be selective to removeparticles bigger than 500 μm.

The lubricant used for roller milling may have low oxygen content and/orcontain a binder. Examples of the lubricant include amide, e.g.,oleamide or amide, or other lower carbon-hydrogenate esters or fattyacid, such as oleic acid.

Powders may be further homogenized by jet milling. In someimplementations, the jet may be formed using air or an inert gas such asHe, Ar, or N. The jet milling may be performed for such time, e.g., 1-4hours, and at such velocity so as to homogenize the mixture and furtherbreak down aggregates of single grains with a size between 1 to 4 Insome implementations, the jet milling may be completed in 24 hours orless.

In some implementations, an 80% reduction in time for the jet milling ofNd—Fe—B powders may be observed compared to jet milling of Nd—Fe—Belemental additives. The average particle size of the magnets may be inthe range of between 4 to 10 During jet milling, the aggregates may bebroken to single grains while an oxidized rare earth powder remainedcoarse, e.g., have a larger particle size. By removing the oxidized rareearth coarse powder, the amount of oxygen incorporated in the startingmagnetic material can be reduced and more preferably suppressed in thefinal magnet. This phase may be done preferably under inert atmosphere,for example using Ar gas, free of any oxygen contamination, with thepurpose of homogenizing the mixture of magnetic powder and freshadditive material of (RE(TM)x) elemental additives and break thesegregated single grains along grain boundaries. RE (rare earth) refersto a combination of any Nd, Pr, Dy, Tb, Y, La, or Sm and TM(transitional elemental additive material) refers to a combination ofany Co, Ni, V, Nb, Mo, Ti, Zr, Al, Cu, Ga, or Fe.

After the particle reduction, mixing, and sieving are completed, thepowder may be aligned and pressed to form a green compact in air or aninert atmosphere. A lubricant may be applied to the powder prior topressing and aligning. The green compact may be pressed and aligned in amagnetic field. Then the green compact may go directly on to sinteringin the range of 1050-1100° C. for 5 hours of holding time, followed byheat treatment at 900° C. for 5 hours and 550° C. for 3 hours. Theselection of sintering temperatures may depend on the amount of totalrare earth additions added prior to the hydrogenation/mixing steps.

In some implementations, hydrogen mixing may be used advantageously tofacilitate homogenization of original material, e.g., from a sinteredmagnet, with fresh elemental additives. This may be followed by jetmilling, which may be used for further homogenization with supplementalmaterials, e.g., rare earth oxides or Nd/Pr, in a process that isamenable to cost efficient scalable processing. Other implementationsmay include milling, roller milling, high energy ball milling, tumblingand other mixing steps.

In some implementations, a method provides for the addition of 0.1 to 19wt. % of one or more rare earth elemental additives to a composition ormethod described herein. In another aspect, a method provides for theaddition of about 0.1 wt. %, about 0.2 wt. %, about 0.3 wt. %, about 0.4wt. %, about 0.5 wt. %, about 1 wt. %, about 2 wt. %, about 3 wt. %,about 4 wt. %, about 5 wt. %, about 6 wt. %, about 7 wt. %, or about 8wt. % of one or more rare earth elemental additives or a combination ofone or more rare earth elemental additives to a composition or methoddescribed herein. In yet another aspect, a method provides for theaddition of about 0.1-0.5 wt. %, about 0.1-1 wt. %, about 0.5-1 wt. %,about 1-2 wt. %, about 1-3 wt. %, about 1-5 wt. %, about 1-8 wt. %,about 2-4 wt. %, about 2-6 wt. %, about 3-5 wt. %, or about 3-8 wt. % ofone or more rare earth elemental additives or a combination of one ormore rare earth elemental additives to a composition or method describedherein.

The foregoing and other embodiments can each optionally include one ormore of the following features, alone or in combination. The method mayinclude performing the fragmenting and the mixing concurrently.Fragmenting may include fragmenting the material to an average particlesize between 1 to 4 μm. Fragmenting may include removing particles witha particle fraction of size bigger than an average size of particles toobtain a low oxygen concentration. Removing particles with the particlefraction of size bigger than the average size of particles to obtain alow oxygen concentration may include sieving.

In some implementations, the method includes mixing the homogeneouspowder with another element selected from the rare earth material R orthe elemental additive A. Fragmenting may include fragmenting to formthe powder with an average particle size between about 1 micron to about2 millimeters. The method may include further fragmenting the powder toan average particle size between about 1 to about 4 microns, andhomogenizing the powder. Homogenizing the powder may includehomogenizing the powder that may include an average particle sizebetween about 1 micron to about 2 millimeters, and mixing the powderwith a) the rare earth material R and b) the elemental additive A toproduce the homogeneous powder may include mixing the powder with anaverage particle size between about 1 to about 4 microns with a) therare earth material R and b) the elemental additive A to produce thehomogeneous powder. Mixing the powder with a) the rare earth material Rand b) the elemental additive A to produce the homogeneous powder mayinclude mixing the powder with an average particle size between about 1micron to about 2 millimeters with a) the rare earth material R and b)the elemental additive A to produce the homogeneous powder, andhomogenizing the powder may include homogenizing the powder that mayinclude an average particle size between about 1 to about 4 microns.

In some implementations, the method includes fragmenting the rare earthmaterial R and the elemental additive A separately to form the powder,wherein mixing the powder with a) the rare earth material R and b) theelemental additive A to produce the homogeneous powder may includemixing the powder with a) the fragmented rare earth material R and b)the fragmented elemental additive A to produce the homogeneous powder.

In some implementations, the method may include sintering andmagnetizing the homogeneous powder to form an Nd—Fe—B magnetic product.Sintering and magnetizing the homogeneous powder to form an Nd—Fe—Bmagnetic product may include compacting the homogeneous powder to form agreen compact, sintering the green compact between about 1000° C. toabout 1100° C., and magnetizing the sintered green compact to an inertatmosphere below 15° C. to form the Nd—Fe—B magnetic product. The methodmay include heat treating the sintered green compact between about 490°C. to about 950° C. prior to magnetizing the sintered green compact. Themethod may include exposing the green compact to an inert magnetic fieldbelow 15° C. An atomic percentage of Co in the Nd—Fe—B magnetic productmay be less than or equal to 3%. An atomic percentage of Cu in theNd—Fe—B magnetic product may be less than or equal to 0.3%. A combinedatomic percentage of Fe and Co in the Nd—Fe—B magnetic product may beless than or equal to 77%. A combined atomic percentage of Nd, Dy, andPr in the Nd—Fe—B magnetic product may be less than or equal to 18 at.%. The method may include adding a lubricant to the powder prior tocompacting the homogeneous powder to form the green compact. Thecoercivity of the Nd—Fe—B magnetic product may be between about 0 toabout 20% greater.

In some implementations, the method may include sintering andmagnetizing the powder to form an Nd—Fe—B magnetic product with a finalcoercivity, wherein the final coercivity is increased by at least 30%.The method may include sintering and magnetizing the powder to form anNd—Fe—B magnetic product with a final coercivity, wherein the finalcoercivity is increased by at least 80%.

In some implementations, the method may include sintering andmagnetizing the homogeneous powder to form an Nd—Fe—B magnetic producthaving a composition substantially of WaRbAc, where W may includeNd—Fe—B material and indices a, b, and c represent atomic percentages ofthe corresponding compositions or elements. Mixing the powder with a)the rare earth material R and b) the elemental additive A to produce thehomogeneous powder may include homogeneously distributing the rare earthmaterial R and the elemental additive A, and sintering and magnetizingthe homogeneous powder to form a Nd—Fe—B magnetic product may includeforming the Nd—Fe—B magnetic product with a concentration of the rareearth material R and a concentration of the elemental additive A thatincreases, on average, surrounding the primary Nd₂Fe₁₄B phase within theNd—Fe—B magnetic product. Forming the Nd—Fe—B magnetic product mayinclude restoring, modifying, and improving a concentration and anelemental composition of a grain boundary phase, on average, at aplurality of grain boundary regions that extend throughout the Nd—Fe—Bmagnetic product.

In some implementations, mixing the powder may include mixing the powderwith at least three elements of: Pr, Nd, Dy, Co, Cu, or Fe. Theelemental additive A may include pure Nd. The elemental additive A mayinclude pure Pr. The method may include adding a lubricant to the powderprior to fragmenting.

The foregoing and other embodiments can each optionally include one ormore of the following features, alone or in combination. The Nd—Fe—Bsintered magnet may exhibits an increase of iHc of greater than about27%, greater than about 60%, or greater than about 83% with respectivedecreases in Br of less than about 0.1%, less than about 3%, and lessthan about 6%. The rare earth material R and the elemental additives Amay be distributed homogeneously throughout the Nd—Fe—B sintered magnetsuch that a concentration of the rare earth material R and aconcentration of the elemental additives A increases on average in amixture of material W surrounding the primary Nd2Fe14B phase within theNd—Fe—B magnet. A atomic percentage of a combination of the rare earthmaterial R and the elemental additives A may include between about 0.1at. % and about 19 at. %. The Nd—Fe—B sintered magnet may include anaverage grain size less than 5 microns. The Nd—Fe—B sintered magnet mayinclude an average grain size less than 2.5 microns. The Nd—Fe—Bsintered magnet may include a density between about 7.56 g/cm³ to about7.6 g/cm³.

In some implementations, the Nd—Fe—B sintered magnet may include anatomic percentage of Co less than or equal to 3%. The Nd—Fe—B sinteredmagnet may include an atomic percentage of Cu less than or equal to0.3%. The Nd—Fe—B sintered magnet may include a combined atomicpercentage of Fe and Co less than or equal to 77%. The Nd—Fe—B sinteredmagnet may include a combined atomic percentage of Nd, Dy, and Pr lessthan or equal to 18%. The elemental additive A may include pure Nd. Theelemental additive A may include pure Pr.

Embodiments of the subject matter and the functional operationsdescribed in this specification can be implemented in digital electroniccircuitry, in tangibly-embodied computer software or firmware, incomputer hardware, including the structures disclosed in thisspecification and their structural equivalents, or in combinations ofone or more of them. Embodiments of the subject matter described in thisspecification can be implemented as one or more computer programs, i.e.,one or more modules of computer program instructions encoded on atangible non transitory program carrier for execution by, or to controlthe operation of, data processing apparatus. Alternatively or inaddition, the program instructions can be encoded on an artificiallygenerated propagated signal, e.g., a machine-generated electrical,optical, or electromagnetic signal, which is generated to encodeinformation for transmission to suitable receiver apparatus forexecution by a data processing apparatus. The computer storage mediumcan be a machine-readable storage device, a machine-readable storagesubstrate, a random or serial access memory device, or a combination ofone or more of them.

The term “data processing apparatus” refers to data processing hardwareand encompasses all kinds of apparatuses, devices, and machines forprocessing data, including by way of example a programmable processor, acomputer, or multiple processors or computers. The apparatus can alsobe, or further include, special purpose logic circuitry, e.g., an FPGA(field programmable gate array) or an ASIC (application specificintegrated circuit). The apparatus can optionally include, in additionto hardware, code that creates an execution environment for computerprograms, e.g., code that constitutes processor firmware, a protocolstack, a database management system, an operating system, or acombination of one or more of them.

A computer program, which may also be referred to or described as aprogram, software, a software application, a module, a software module,a script, or code, can be written in any form of programming language,including compiled or interpreted languages, or declarative orprocedural languages, and it can be deployed in any form, including as astandalone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A computer program may, butneed not correspond to a file in a file system. A program can be storedin a portion of a file that holds other programs or data, e.g., one ormore scripts stored in a markup language document, in a single filededicated to the program in question, or in multiple coordinated files,e.g., files that store one or more modules, sub programs, or portions ofcode. A computer program can be deployed to be executed on one computeror on multiple computers that are located at one site or distributedacross multiple sites and interconnected by a communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable computers executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Computers suitable for the execution of a computer program include, byway of example, general or special purpose microprocessors or both, orany other kind of central processing unit. Generally, a centralprocessing unit will receive instructions and data from a read onlymemory or a random access memory or both. The essential elements of acomputer are a central processing unit for performing or executinginstructions and one or more memory devices for storing instructions anddata. Generally, a computer will also include, or be operatively coupledto receive data from or transfer data to, or both, one or more massstorage devices for storing data, e.g., magnetic, magneto optical disks,or optical disks. However, a computer need not have such devices.Moreover, a computer can be embedded in another device, e.g., a mobiletelephone, a personal digital assistant (PDA), a mobile audio or videoplayer, a game console, a Global Positioning System (GPS) receiver, or aportable storage device, e.g., a universal serial bus (USB) flash drive,to name just a few.

Computer readable media suitable for storing computer programinstructions and data include all forms of non volatile memory, mediaand memory devices, including by way of example semiconductor memorydevices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks,e.g., internal hard disks or removable disks; magneto optical disks; andCD ROM and DVD-ROM disks. The processor and the memory can besupplemented by, or incorporated in, special purpose logic circuitry.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input. In addition, a computer can interact with a user bysending documents to and receiving documents from a device that is usedby the user; for example, by sending web pages to a web browser on auser's device in response to requests received from the web browser.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front end component, e.g., aclient computer having a graphical user interface or a Web browserthrough which a user can interact with an implementation of the subjectmatter described in this specification, or any combination of one ormore such back end, middleware, or front end components. The componentsof the system can be interconnected by any form or medium of digitaldata communication, e.g., a communication network. Examples ofcommunication networks include a local area network (LAN) and a widearea network (WAN), e.g., the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other. In someembodiments, a server transmits data, e.g., an HTML page, to a userdevice, e.g., for purposes of displaying data to and receiving userinput from a user interacting with the user device, which acts as aclient. Data generated at the user device, e.g., a result of the userinteraction, can be received from the user device at the server.

An example of one such type of computer is shown in FIG. 18, which showsa schematic diagram of a generic computer system 1800. The system 1800can be used for the operations described in association with any of thecomputer-implement methods described previously, according to oneimplementation. The system 1800 includes a processor 1810, a memory1820, a storage device 1830, and an input/output device 1840. Each ofthe components 1810, 1820, 1830, and 1840 are interconnected using asystem bus 1850. The processor 1810 is capable of processinginstructions for execution within the system 1800. In oneimplementation, the processor 1810 is a single-threaded processor. Inanother implementation, the processor 1810 is a multi-threadedprocessor. The processor 1810 is capable of processing instructionsstored in the memory 1820 or on the storage device 1830 to displaygraphical information for a user interface on the input/output device1840.

The memory 1820 stores information within the system 1800. In oneimplementation, the memory 1820 is a computer-readable medium. In oneimplementation, the memory 1820 is a volatile memory unit. In anotherimplementation, the memory 1820 is a non-volatile memory unit.

The storage device 1830 is capable of providing mass storage for thesystem 1800. In one implementation, the storage device 1830 is acomputer-readable medium. In various different implementations, thestorage device 1830 may be a floppy disk device, a hard disk device, anoptical disk device, or a tape device.

The input/output device 1840 provides input/output operations for thesystem 1800. In one implementation, the input/output device 1840includes a keyboard and/or pointing device. In another implementation,the input/output device 1840 includes a display unit for displayinggraphical user interfaces.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinvention or on the scope of what may be claimed, but rather asdescriptions of features that may be specific to particular embodimentsof particular inventions. Certain features that are described in thisspecification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable subcombination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a subcombination or variation of a sub combination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various system modulesand components in the embodiments described above should not beunderstood as requiring such separation in all embodiments, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

Particular embodiments of the subject matter have been described. Otherembodiments are within the scope of the following claims. For example,the actions recited in the claims can be performed in a different orderand still achieve desirable results. As one example, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In some cases, multitasking and parallel processing may beadvantageous.

What is claimed is:
 1. A sintered body comprising grains and a grainboundary composition, wherein: (a) the grains comprise a compositionrepresented by a formula G₂M₁₄B, where G is Nd, Dy, Pr, Tb, or acombination thereof, and M is Co, Fe, Ni, or a combination thereof,wherein the grains are optionally doped with one or more rare earthelements; and (b) the grain boundary composition is an alloy compositionrepresented by the formula:Nd_(8.5-12.5)Dy₃₅₋₄₅Co₃₂₋₄₁Cu_(3-6.5)Fe_(1.5-5), wherein the subscriptvalues are atom percent relative to the total composition of the alloycomposition.
 2. The sintered body of claim 1, wherein G comprises Nd. 3.The sintered body of claim 1, wherein G comprises Dy.
 4. The sinteredbody of claim 1, wherein G comprises Pr.
 5. The sintered body of claim1, wherein G comprises Tb.
 6. The sintered body of claim 1, wherein Mcomprises Fe.
 7. The sintered body of claim 1, wherein M comprises Co.8. The sintered body of claim 1, wherein M comprises Ni.
 9. The sinteredbody of claim 1, wherein the grains comprise one or more of (i)Nd₂Fe₁₄B; (ii) Dy₂Fe₁₄B: (iii) Pr₂Fe₁₄B; (iv) Tb₂Fe₁₄B; (v) Nd₂Co₁₄B;(vi) Pr₂Co₁₄B; (vii) Tb₂Co₁₄B; (viii) Nd₂Ni₁₄B; (ix) Pr₂Ni₁₄B; (x)Tb₂Ni₁₄B.
 10. The sintered body of claim 1, wherein the grains are dopedwith one or of Nd, Gd, Tb, La, Ce, Yb, Ho, or Eu.
 11. The sintered bodyof claim 1 having an oxygen content of less than 1.98 atom %.
 12. Thesintered body of claim 1 that is magnetic.
 13. The sintered body ofclaim 1 that exhibits, at 25° C.: (a) a remanence (Br) in a range offrom 1.29 T to 1.423 T; (b) a coercivity (iHc) in a range of from 1042kA/m to 1900 kA/m; (c) an energy product (BH_(max)) in a range of from323 kJ/m³ to 391 kJ/m³; or (d) a combination of two or more of (a) to(c).
 14. A device comprising a sintered body of claim 1, the devicebeing a starter motor, anti-lock braking system, fuel pump, fan,loudspeaker, microphone, telephone ringer, switch, relay, hard-diskdrive, stepper motor, servo-motor, magnetic resonance imager, windmillgenerator, robot, electronic sensor, magnetic separator, guidancesystem, or a satellite.
 15. A population of particles comprising: (a) afirst fractional population of demagnetized particles represented by aformula G₂M₁₄B, where G is Nd, Dy, Pr, Tb, or a combination thereof, andM is Co, Fe, Ni, or a combination thereof, wherein the demagnetizedparticles are optionally doped with one or more rare earth elements; and(b) a second fractional population of additive particles represented bya composite formula: Nd_(8.5-12.5)Dy₃₅₋₄₅Co₃₂₋₄₁Cu_(3-6.5)Fe_(1.5-5),wherein the subscript values are atom percent relative to the totalcomposition of the additive particles.
 16. The population of particlesof claim 15, wherein the demagnetized particles are optionally dopedwith one or more of Nd, Pr, Dy, Gd, Tb, La, Ce, Yb, Ho, or Eu.
 17. Thepopulation of particles of claim 15, wherein the first and secondfractional populations of particles are compressed in a green body. 18.The population of particles of claim 17, wherein the first and secondfractional populations of particles are uniformly distributed in thegreen body.